FFRCT and recurrent symptoms in patients with stable chest pain

Introduction

The major benefit of coronary revascularization when compared with optimal medical treatment (OMT) in patients with stable chest pain (CP) relates to improvement of symptoms and reduction of reinterventions. Non-invasive methods are warranted to discriminate between patients at low and high risk of recurrent CP for subsequent guidance of antianginal treatment (invasive or OMT).

Purpose

To evaluate the association between coronary CT angiography (CTA) derived fractional flow reserve (FFRCT), recurrent CP and quality of life (QOL) in patients with new onset stable CP and stenosis by CTA.

Methods

Multicenter cohort 3-year follow-up sub-study of 769 patients from the Assessing Diagnostic Value of Non-invasive FFRCT in Coronary Care (ADVANCE) registry at three Danish sites, the “ADVANCE-DK Registry”. All patients had at least one ≥30% coronary stenosis by CTA and underwent subsequent core laboratory FFRCT analysis by HeartFlow. An abnormal FFRCT was defined as the lowest in vessel FFRCT value ≤0.80. Patients were classified according to completeness of revascularization by FFRCT: 1) completely revascularized (CR-FFRCT), all coronary arteries with an abnormal FFRCT test result revascularized; 2) incompletely revascularized (IR-FFRCT), ≥1 coronary artery with an abnormal FFRCT test result not revascularized. All patients completed the Seattle Angina Questionnaire (SAQ-7), the EuroQol questionnaire (EQ-5D-5L) and graded (0–100) overall health using the EQ VAS scale at 3-year follow-up. Recurrent CP was defined as CP within the last 4 weeks prior to this follow-up.

Results

Patient characteristics are given in Table 1. At follow-up 23% patients reported recurrent CP. An abnormal vs a normal FFRCT increased the risk of recurrent CP, 27% vs 15%, RR: 1.82; 95% CI: 1.31–2.52, p<0.001. Amongst patients with abnormal FFRCT, revascularization (+/−) was associated to a numerical, but not statistical significantly, reduced risk of recurrent CP, 23% vs 30%, RR: 0.76; 95% CI: 0.56–1.03, p=0.07. IR-FFRCT vs CR-FFRCT had a higher risk for recurrent CP, 31% vs 13%, RR: 2.34; 95% CI: 1.48–3.68, p<0.001, whilst no difference was observed for CR-FFRCT vs normal FFRCT, 13% vs 15%, RR: 0.92; 95% CI: 0.54–1.54, p=0.74. IR-FFRCT vs CR-FFRCT or normal FFRCT, had lower SAQ-7, EQ-5D-5L and EQ-VAS scores, Table 1, all p<0.005. Scores for three selected SAQ-7 domains are shown in Figure 1. Use of antianginal medicine was higher in IR-FFRCT compared to CR-FFRCT and normal FFRCT, mean ± SD: 1.2±0.05 vs 1.0±0.04, p=0.02.

Conclusion

An abnormal FFRCT identifies patients with an increased risk of recurrent CP up to 3 years after index testing. Completeness of revascularization by FFRCT reclassifies patients with abnormal FFRCT into groups with low and high risk for recurrent CP and impaired QOL.

Funding Acknowledgement

Type of funding sources: None.

P6175Prediction of coronary revascularization by coronary computed tomography angiography derived fractional flow reserve - different algorithms for interpretation

Introduction

Coronary CT angiography (CTA) derived fractional flow reserve (FFRct) is increasingly used for guiding referral to invasive procedures in patients with stable chest pain. However, optimal interpretation of FFRct-analysis in terms of location and threshold of applied FFRct-values is unclear.

Purpose

To evaluate the clinical performance of various vessel-specific physiological FFRct derived measures of ischemia for prediction of standard of care guided coronary revascularization in patients with stable chest pain and coronary artery disease as determined by coronary CTA.

Methods

Retrospective study in patients with stable chest pain referred for coronary angiography based on coronary CTA. Standard acquired coronary CTA data sets were transmitted for core-laboratory analysis at HeartFlow. Any FFRct value in the major coronary arteries ≥1.8 mm in diameter, including side branches, were registered. Lesions were categorized as positive for ischemia using 6 different algorithms: Lowest in vessel FFRct-value (1) ≤0.75 or (2) ≤0.80; 2 cm distal-to-lesion FFRct-value (3) ≤0.75 or (4) ≤0.80; ΔFFRct (5) ≥0.06 or a combination of 2 and 5. The personnel responsible for downstream patient management had no information regarding FFRct test results.

Results

A total of 172 patients were included. Revascularization was performed in 62 (35%) patients. The diagnostic performance of different FFRct algorithms for predicting standard of care guided coronary revascularization is shown in the Table.

Revascularization Predictions by FFRct N=172 Diagnostic performance FFRCT false negative FFRCT false positive Values given as (%) No. of revasc vessels No. of abnormal vessels FFRCT Algorithm Sens Spec PPV NPV Acc 1 2 3 1 2 3 Distal FFRCT ≤0.75 77 68 58 84 72 12 2 0 29 5 1 Distal FFRCT ≤0.80 92 43 48 90 61 5 0 0 40 20 3 Lesion-specific FFRCT ≤0.75 68 86 74 83 80 17 3 0 12 3 0 Lesion-specific FFRCT ≤0.80 82 78 68 89 80 10 2 0 21 3 1 ΔFFRCT ≥0.06 98 36 47 98 59 1 0 0 51 19 0 Combinationa 92 54 53 92 67 5 0 0 39 12 0 aDistal FFRCT ≤0.80 and ΔFFRCT ≥0.06. Sens = sensitivity; Spec = specificity; PPV = positive predictive value; NPV = negative predictive value; Acc = accuracy; FFRCT = fractional flow reserve derived from coronary CTA; ΔFFRCT = difference between FFRCT-value immediately proximal and distal to lesion; Revasc = revascularized.

Conclusion

The diagnostic performance of FFRct in terms of predicting standard of care guided coronary revascularization is dependent on the applied algorithm for interpretation of the FFRct-analysis.

P6186Symptomatic effect of coronary revascularization at 1-year follow-up in stable chest pain - prediction by coronary computed tomography angiography derived fractional flow reserve

Introduction

Coronary CT angiography (CTA) derived fractional flow reserve (FFRct) is increasingly being used for guiding referral to invasive procedures in patients with stable chest pain. However, the ability of FFRct to predict the symptomatic effect of revascularization remains unclear.

Purpose

To evaluate the ability of different vessel-specific physiological FFRct derived measures of ischemia for predicting the occurrence of chest pain one year after coronary revascularization in stable patients.

Methods

Retrospective study in patients with stable chest pain referred for coronary angiography based on coronary CTA. Standard acquired coronary CTA data sets were transmitted for core-laboratory analysis at HeartFlow. Patients were categorized as positive for ischemia using 3 different algorithms: Lowest in vessel FFRct-value ≤0.80; ΔFFRct ≥0.06 or a combination of the two. Personnel responsible for downstream patient management had no information on FFRct test results. Classification of revascularization was performed based on the applied FFRct algorithm: complete if all FFRct positive lesions were revascularized; incomplete if ≥1 FFRct positive lesion was not revascularized. Symptomatic status at 1-year follow-up was obtained by a visit in the outpatient clinic or by telephone.

Results

A total of 172 patients were included. Revascularization was performed in 62 (35%) patients. At 1-year follow-up 48 (28%) patients had chest pain; 15 (24%) revascularized vs 33 (30%) non-vascularized patients, p=0.415. No difference in utilization of anti-anginal medicine for patients with and without chest pain was registered at 1-year follow-up. The association between the chosen FFRct algorithm, revascularization and occurrence of chest pain at 1-year follow-up are shown in the Table.

FFRct, Revascularization and Chest pain FFRCT, Algorithm Revascularizationb Patients with chest pain 1-year risk of chest pain p-valuec N (%) OR (95%-CI) Distal FFRCT ≤0.80 Incomplete 32 (34) Ref. Distal FFRCT ≤0.80 Complete 4 (15) 0.34 (0.11, 1.06) Distal FFRCT >0.80 No 11 (24) 0.61 (0.27, 1.35) 0.097 ΔFFRCT ≥0.06 Incomplete 34 (35) Ref. ΔFFRCT ≥0.06 Complete 7 (21) 0.49 (0.19, 1.24) ΔFFRCT <0.06 No 7 (18) 0.41 (0.16, 1.03) 0.074 Combinationa abnormal Incomplete 30 (40) Ref. Combination abnormal Complete 6 (18) 0.32 (0.12, 0.87) Combination normal No 11 (19) 0.35 (0.16, 0.78) 0.009 aDistal FFRCT ≤0.80 and ΔFFRCT ≥0.06. bIncomplete (≥1 FFRCT positive lesion not revascularized); complete (All FFRCT positive lesions revascularized); No (No FFRCT positive lesions and revascularization not performed). cBetween group comparison performed using logistic regression.

Conclusion

Revascularization based on classification by FFRct is associated with symptomatic relief at 1-year follow-up in patients with stable chest pain.

P706Treatment of hypercholesterolaemia with PCSK-9 Inhibitors in Denmark. Assessment of real-life data; safety an extent of adverse effects after the first years of clinical use

Introduction

PCSK9 Inhibitors (PCSK9 I) are a new group of drugs for treatment of hyperlipidaemia. These drugs have been available in Denmark since October 2015. From the two existing major outcome studies (FOURIER and ODYSSEY OUTCOMES) it has been shown that there was no significant difference in the risk of serious adverse events, discontinuation due to adverse events, neurocognitive events, diabetes-related events, muscle-related events, or myalgia in the treatment group, compared with the control group. In FOUIRER 12.5% came of treatment; In ODYSSEY the rate was 10.2–14.8%. Although this highlights the efficacy and safety in patients with cardiovascular disease, we have little knowledge of the use, efficacy and safety with these drugs in real-life populations

Purpose

We aim to describe the demography, the treatment efficacy and the extent of adverse effects among patients treated in Danish lipid clinics.

Methods

Data on all patients treated with PCSK9 I between October 1st, 2015 and May 1st, 2018 were obtained from lipid clinics in Denmark. A database containing information on medications before treatment, adverse effects, plasma lipids (LDL-C, Triglyceride, High density lipoprotein cholesterol (HDL-C)) and supplementary blood tests was created. Levels of plasma lipids and organ markers (Creatinine, Hba1c or Alanine aminotransferase (ALAT)) at baseline and at follow up visits were analysed.

Results

Nationwide, 383 patients were included, an estimated 90% of all patients undergoing treatment with PCSK9 I in Denmark. A large proportion (n=243 - 63.4%) were described as statin intolerant and only 94 patients were receiving statins at baseline. Adverse effects (AE) were reported by 71 patients (18.5%) on PCSK9 I therapy and 50 patients (13.1%) stopped treatment. Most common AE were flu like symptoms and musculoskeletal aches. In two cases an increase in serum creatinine kinase was detected. One case of angioedema and three cases of local reactions to injections had been documented. No case of anaphylaxis was reported. Of the 71 patients with AEs 55 (77.5%) were statin intolerant. Of the 50, who came off treatment, 43 (86.0%) were statin intolerant. When treatment was stopped 15 patients (30.0%) tried the alternative PCSK9 Inhibitor (cross over). Of those, nine patients were able to tolerate the alternative PCSK9 I treatment.

Conclusion

Many patients (18.3%) reported AEs on a wide range of symptoms, but the rate of patients terminating PCSK9 I treatment was the same as found in the outcome studies (13.1% vs. 12.2 and 10.2–14.8%). Most of the patients who stopped treatment were statin intolerant and produced the same symptoms, as they had experienced with statins. Interestingly, nine of the 15 patients that were switched to the alternate PCSK9 I seems to tolerate this treatment.

2981Treatment of Hypercholesterolaemia with PCSK9 Inhibitors in Denmark. Assessment of real-life data; Extent and Efficacy after the first years of clinical use

Introduction

Proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9 I) are a new group of drugs for treatment of hypercholesterolaemia. At present there are two available drugs evolocumab and alirocumab, which lowers low-density lipoprotein cholesterol (LDL-C) by inhibiting the enzyme proprotein convertase subtilisin/kexin type 9. Both evolocumab and alirocumab outcome data (FOURIER and ODYSSEY OUTCOMES respectively) have shown a reduced risk of myocardial infarction, stroke, and coronary revascularization without adverse effects. Patients included in these trials had existing atherosclerotic cardiovascular disease and all patients received maximum-tolerated statin. In the FOURIER trail 100% of the patients received statin and 69% high intensity statin, in the ODYSSEY trial is was 98% and 89%, respectively

Purpose

In collaboration with lipid clinics in Denmark we aimed to describe the clinical characteristics of patients treated, along with the efficacy of LDL-C reduction of such treatment in a real-life population.

Methods

We contacted lipid and cardiological clinics throughout Denmark and obtained clinical data on the majority of patients treated with PCSK9 I in Denmark between October 1st, 2015 and May 1st, 2018. A database containing information on medical history, medications used prior to PCSK9 I initiation, adverse events and plasma lipids including LDL-C was created. Records of baseline LDL-C and at follow up visits were analysed.

Results

From October 1st 2015 to may 1st2018, 383 patients were enrolled; an estimated 90% of all patients in Denmark. The distribution of clinical indications for PCSK9 I initiation is shown in figure 1. A total 243 of these patients (63.4%) were characterised as statin intolerant and 225 (58.7%) had familial hypercholesterolaemia. More than two thirds (69.5%) of the patients were given PCSK9 Inhibitors as secondary prophylaxis. Overall LDL was significantly reduced from 5.11 mmol/L (CI [4.95; 5.28]) to 2.46 mmol/L (CI [2.33–2.68]) after the first month of treatment, corresponding to a 48.9% decrease in LDL-C, which persisted without significant changes throughout the two years of observation. Even with this reduction, only about half of the population of both primary and secondary prevention reached their treatment target. This remained unchanged in patients with familial hypercholesterolaemia an those with statin intolerance (Table 1). A subgroup analysis showed a significantly lower LDL in the first 12 months when PCSK9 I were combined with statins versus PCSK9 I as monotherapy (p<0.05) (results not shown).

Conclusion

Patients treated with PCSK9 I in this real-life do not resemble the populations in the major endpoint studies, as the majority in this real-life population are statin intolerant. Nevertheless, we see an overall reduction of LDL of approx. 50%, even though the number of patients reaching their treatment target remains low (approx. 50% at best).

Prediction of Coronary Revascularization in Stable Angina: Comparison of FFRCT With CMR Stress Perfusion Imaging

OBJECTIVES

This study was designed to compare head-to-head fractional flow reserve (FFR) derived from coronary computed tomography angiography (CTA) (FFR_CT) and cardiac magnetic resonance (CMR) stress perfusion imaging for prediction of standard-of-care-guided coronary revascularization in patients with stable chest pain and obstructive coronary artery disease by coronary CTA.

BACKGROUND

FFR_CT is a novel modality for noninvasive functional testing. The clinical utility of FFR_CT compared to CMR stress perfusion imaging in symptomatic patients with coronary artery disease is unknown.

METHODS

Prospective study of patients (n = 110) with stable angina pectoris and 1 or more coronary stenosis ≥50% by coronary CTA. All patients underwent invasive coronary angiography. Revascularization was FFR-guided in stenoses ranging from 30% to 90%. FFR_CT ≤0.80 in 1 or more coronary artery or a reversible perfusion defect (≥2 segments) by CMR categorized patients with ischemia. FFR_CT and CMR were analyzed by core laboratories blinded for patient management.

RESULTS

A total of 38 patients (35%) underwent revascularization. Per-patient diagnostic performance for identifying standard-of-care-guided revascularization, (95% confidence interval) yielded a sensitivity of 97% (86% to 100%) for FFR_CT versus 47% (31% to 64%) for CMR, p < 0.001; corresponding specificity was 42% (30% to 54%) versus 88% (78% to 94%), p < 0.001; negative predictive value of 97% (91% to 100%) versus 76% (67% to 85%), p < 0.05; positive predictive value of 47% (36% to 58%) versus 67% (49% to 84%), p < 0.05; and accuracy of 61% (51% to 70%) versus 74% (64% to 82%), p > 0.05, respectively.

CONCLUSIONS

In patients with stable chest pain referred to invasive coronary angiography based on coronary CTA, FFR_CT and CMR yielded similar overall diagnostic accuracy. Sensitivity for prediction of revascularization was highest for FFR_CT, whereas specificity was highest for CMR.

The Danish Cardiac Rehabilitation Database

Aim of database

The Danish Cardiac Rehabilitation Database (DHRD) aims to improve the quality of cardiac rehabilitation (CR) to the benefit of patients with coronary heart disease (CHD).

Study population

Hospitalized patients with CHD with stenosis on coronary angiography treated with percutaneous coronary intervention, coronary artery bypass grafting, or medication alone. Reporting is mandatory for all hospitals in Denmark delivering CR. The database was initially implemented in 2013 and was fully running from August 14, 2015, thus comprising data at a patient level from the latter date onward.

Main variables

Patient-level data are registered by clinicians at the time of entry to CR directly into an online system with simultaneous linkage to other central patient registers. Follow-up data are entered after 6 months. The main variables collected are related to key outcome and performance indicators of CR: referral and adherence, lifestyle, patient-related outcome measures, risk factor control, and medication. Program-level online data are collected every third year.

Descriptive data

Based on administrative data, approximately 14,000 patients with CHD are hospitalized at 35 hospitals annually, with 75% receiving one or more outpatient rehabilitation services by 2015. The database has not yet been running for a full year, which explains the use of approximations.

Conclusion

The DHRD is an online, national quality improvement database on CR, aimed at patients with CHD. Mandatory registration of data at both patient level as well as program level is done on the database. DHRD aims to systematically monitor the quality of CR over time, in order to improve the quality of CR throughout Denmark to benefit patients.

Invasively Measured Aortic Systolic Blood Pressure and Office Systolic Blood Pressure in Cardiovascular Risk Assessment

Aortic systolic blood pressure (BP) represents the hemodynamic cardiac and cerebral burden more directly than office systolic BP. Whether invasively measured aortic systolic BP confers additional prognostic value beyond office BP remains debated. In this study, office systolic BP and invasively measured aortic systolic BP were recorded in 21 908 patients (mean age: 63 years; 58% men; 14% with diabetes mellitus) with stable angina pectoris undergoing elective coronary angiography during January 2001 to December 2012. Multivariate Cox models were used to assess the association with incident myocardial infarction, stroke, and death. Discrimination and reclassification were assessed using Harrell’s C and the Continuous Net Reclassification Index. Data were analyzed with and without stratification by diabetes mellitus status. During a median follow-up period of 3.7 years (range: 0.1–10.8 years), 422 strokes, 511 myocardial infarctions, and 1530 deaths occurred. Both office and aortic systolic BP were associated with stroke in patients with diabetes mellitus (hazard ratio per 10 mm Hg, 1.18 [95% confidence interval, 1.07–1.30] and 1.14 [95% confidence interval, 1.05–1.24], respectively) and with myocardial infarction in patients without diabetes mellitus (hazard ratio, 1.07 [95% confidence interval, 1.02–1.12] and 1.05 [95% confidence interval, 1.01–1.10], respectively). In models including both BP measurements, aortic BP lost statistical significance and aortic BP did not confer improvement in either C-statistics or net reclassification analysis. In conclusion, invasively measured aortic systolic BP does not add prognostic information about cardiovascular outcomes and all-cause mortality compared with office BP in patients with stable angina pectoris, either with or without diabetes mellitus.

Primary structure of the (1-->3,1-->4)-beta-D-glucan 4-glucohydrolase from barley aleurone

During germination of barley grains, the cell walls of the starchy endosperm are degraded by (1-->3,1-->4)-beta-glucanases (EC 3.2.1.73) secreted from the aleurone and scutellar tissues. The complete sequence of the aleurone (1-->3,1-->4)-beta-glucanase isoenzyme II comprises 306 amino acids and was determined by sequencing nine tryptic peptides (110 residues) and aligning them with the amino acid sequence deduced from a cDNA clone encoding the 291 NH(2)-terminal residues. Although no amino acid sequence homology with a bacterial (1-->3)(1-->4)-beta-glucanase is apparent, close to 50% homology is found with two large regions of a (1-->3)-beta-glucanase from tobacco pith tissue. The gene for barley (1-->3,1-->4)-beta-glucanase isoenzyme II shares with that for the alpha-amylase isoenzyme 1 a strongly preferred use of codons with G and C in the wobble position (94% and 90%, respectively). Both enzymes are secreted from the aleurone cells during germination. Such one-sided codon usage is not characteristic for the gene encoding the (1-->3)-beta-glucanase of tobacco pith tissue or the hor2-4 gene encoding the B(1) hordein storage protein in the endosperm.

Secular trends in acute myocardial infarction in relation to physical activity in the general Danish population

Secular trends in AMI rates were analyzed in relation to physical activity levels. The population attributable risk of physical inactivity was calculated. Participants were randomly selected subjects from a suburb of Copenhagen, Denmark, screened during the years 1964-1991. Occupational physical activity and in leisure time were assessed 1964, 1974, 1976, 1982, 1987 and 1991 by self-administered questionnaire along with smoking habits and alcohol consumption. Blood pressure, weight, height and serum lipids were measured according to WHO-standards. Mortality data were obtained from death certificates, from hospital records or autopsies. Acute myocardial infarctions (AMI) 1964-1994 were included. 13.925 men and women aged 30, 40, 50 and 60 years, were drawn as random samples from a background population of 300.000 inhabitants. A cohort born in 1914 was examined in 1964 and 1974, a cohort born in 1936, was examined in 1976 and 1987; Monica (Monitoring trends and determinants in cardiovascular diseases) I cohort were examined in 1982 and 1987; MONICA II in 1986, and MONICA III in 1991. Mean physical activity level at leisure adjusted for age and sex increased over time (P < 0001). 25% of the men were sedentary, and more women reported a sedentary lifestyle than men. The overall trend was from 1964 to 1992 a decline in physical activity at work (P < 0001) in both gender and all age groups. The difference in AMI incidence rates between leisure time physical activity (LTPA) levels increased over time. No change was found in AMI rates comparing sedentary in different time periods. A remarkable decrease over time in the AMI incidence rate was found in physically active during leisure time. Population attributable risk (PAR) exceeded 40% in both genders in the late 1980s. In conclusion the difference in AMI rates between LTPA subgroups has increased over time. The low AMI rates observed among the most physically active reveal a substantial potential for the prevention of AMI through physical activity. A population attributable risk of more than 40% for physical inactivity suggests a potential for primary prevention through increased physical activity.

Isolation, enzymatic properties, and mode of action of an exo-1,3-beta-glucanase from Trichoderma viride

An exo-1,3-beta-glucanase has been isolated from cultural filtrate of T. viride AZ36. The N-terminal sequence of the purified enzyme (m = 61 +/- 1 kDa) showed no significant homology to other known glucanases. The 1,3-beta-glucanase displayed high activity against laminarins, curdlan, and 1,3-beta-oligoglucosides, but acted slowly on 1,3-1,4-beta-oligoglucosides. No significant activity was detected against high molecular mass 1,3-1,4-beta-glucans. The enzyme carried out hydrolysis with inversion of the anomeric configuration. Whereas only glucose was released from the nonreducing terminus during hydrolysis of 1,3-beta-oligoglucosides, transient accumulation of gentiobiose was observed during hydrolysis of laminarins. The gentiobiose was subsequently degraded to glucose. The Michaelis constants Km and Vmax have been determined for the hydrolysis of 1,3-beta-oligoglucosides with degrees of polymerization ranging from 2 to 6. Based on these data, binding affinities for subsites were calculated. Substrate binding site contained at least five binding sites for sugar residues.

A novel type of arabinoxylan arabinofuranohydrolase isolated from germinated barley analysis of substrate preference and specificity by nano-probe NMR

An arabinoxylan arabinofuranohydrolase was isolated from barley malt. The enzyme preparation, Ara 1, contained two polypeptides with apparent molecular masses of approximately 60 and approximately 66 kDa, a pI of 4.55 and almost identical N-terminal amino-acid sequences. With p-nitrophenyl alpha-L-arabinofuranoside (pNPA) as substrate, Ara 1 exhibited a Km of 0.5 mM and a Vmax of 6.7 micromol. min-1.(mg of protein)-1. Maximum activity was displayed at pH 4.2 and 60 degrees C, and, under these conditions, the half-life of the enzyme was 8 min. The Ara 1 preparation showed no activity against p-nitrophenyl alpha-L-arabinopyranoside or p-nitrophenyl beta-D-xylopyranoside. Substrate preference and specificity were investigated using pure oligosaccharides and analysis by TLC and nano-probe NMR. Ara 1 released arabinose from high-molecular-mass arabinoxylan and arabinoxylan-derived oligosaccharides but was inactive against linear or branched-chain arabinan. Arabinose was readily released from both singly and doubly substituted xylo-oligosaccharides. Whereas single 2-O-linked and 3-O-linked arabinose substituents on non-reducing terminal xylose were released at similar rates, there was a clear preference for 2-O-linked arabinose on internal xylose residues. When Ara 1 acted on oligosaccharides with doubly substituted, non-reducing terminal xylose, the 3-O-linked arabinose group was preferred as the initial point of attack. Oligosaccharides with doubly substituted internal xylose were poor substrates and no preference could be determined. The enzyme described here is the first reported arabinoxylan arabinofuranohydrolase which is able to release arabinose from both singly and doubly substituted xylose, and it hydrolyses p-nitrophenyl alpha-L-arabinofuranoside at a rate similar to that observed for oligosaccharide substrates.

Application of nano-probe NMR for structure determination of low nanomole amounts of arabinoxylan oligosaccharides fractionated by analytical HPAEC-PAD

A methodology for NMR analysis of low nanomole amounts of oligosaccharides fractionated by analytical HPAEC is presented. Arabinoxylan derived oligosaccharides purified by HPAEC-PAD on an analytical column, by single injections, were analyzed with nano-probe NMR and MALDI-TOF MS to provide full structural assignment. The NMR data were obtained with a 500 MHz NMR spectrometer equipped with a 1H-observe nano-probe. Both one- and two-dimensional experiments on arabinoxylan samples in the low nanomole range were performed, including 1H-1H DQF-COSY, 1H-1H TOCSY and 1H-1H ROESY. These experiments allowed, in combination with MALDI-TOF MS and literature NMR data, a complete structural determination of several tetra-, penta-, hexa- and heptasaccharides. Two new structures: alpha-L-Araf-(1 --> 2)-beta-D-Xylp-(1 --> 4)-beta-D-Xylp-(1 --> 4)-beta-D-Xylp-(1 --> 4)-D-Xylp and alpha-L-Araf-(1 --> 2)[alpha-L-Araf-(1 --> 3)]-beta-D-Xylp-(1 --> 4)-beta-D-Xylp-(1 --> 4)-beta-D-Xylp-(1 --> 4)-D-Xylp) were characterized, as well as some previously published structures.

A highly thermostable endo-(1,4)-beta-mannanase from the marine bacterium Rhodothermus marinus

Rhodothermus marimus ATCC 43812, a thermophilic bacterium isolated from marine hot springs, possesses hydrolytic activities for depolymerising substrates such as carob-galactomannan. Screening of expression libraries identified mannanase-positive clones. Subsequently, the corresponding DNA sequences were determined, eventually identifying a coding sequence specifying a 997 amino acid residue protein of 113 kDa. Analyses revealed an N-terminal domain of unknown function and a C-terminal mannanase domain of 550 amino acid residues with homology to known mannanases of glycosidase family 26. Action pattern analysis categorised the R. marinus mannanase as an endo-acting enzyme with a requirement for at least five sugar moieties for effective catalytic activity. When expressed in Escherichia coli, purified gene product with catalytic activity was mainly found as two protein fragments of 45 kDa and 50 kDa. The full-length protein of 113 kDa was only detected in crude extracts of R. marinus, while truncated protein-containing fractions of the original source resulted in a major active protein of 60 kDa. Biochemical analysis of the mannanase revealed a temperature and pH optimum of 85 degrees C and pH 5.4, respectively. Purified, E. coil-produced protein fragments showed high heat stability, retaining more than 70% and 25% of the initial activity after 1 h incubation at 70 degrees C and 90 degrees C, respectively. In contrast, R. marinus-derived protein retained 87% activity after 1 h at 90 degrees C. The enzyme hydrolysed carob-galactomannan (locust bean gum) effectively and to a smaller extent guar gum, but not yeast mannan.

Purification and characterization of barley dipeptidyl peptidase IV

Barley (Hordeum vulgare L.) storage proteins, which have a high content of proline (Pro) and glutamine, are cleaved by cysteine endoproteases to yield peptides with a Pro next to the N-terminal and/or C-terminal amino acid residues. A peptidase cleaving after Xaa-Pro- at the N terminus of peptides was purified from green barley malt. It was identified as a serine-type dipeptidyl peptidase (DPP), based on inhibitor studies, and the nature of the cleavage product. It is a monomeric glycoprotein with an apparent molecular mass of 105 kD (85 kD after deglycosylation), with a pI of 3.55 and a pH optimum at 7.2. Substrate specificity was determined with a series of fluorogenic peptide substrates with the general formula Xaa-Pro-AMC, where Xaa is an unspecified amino acid and AMC is 7-amino-4-methylcoumarin. The best substrates were Xaa = lysine and arginine, while the poorest were Xaa = aspartic acid, phenylalanine, and glutamic acid. The K(m) values ranged from 0.071 to 8.9 microM, compared with values of 9 to 130 microM reported for mammalian DPP IVs. We discuss the possible role of DPP IV in the degradation of small Pro-containing peptides transported from the endosperm to the embryo of the germinating barley grain.

A transglycosylating 1,3(4)-beta-glucanase from rhodothermus marinus NMR analysis of enzyme reactions

The enzymatic hydrolysis of polysaccharides by the 1, 3(4)-beta-glucanase (LamR) from Rhodothermus marinus has been explored. The enzyme cleaves the 1,3-beta-linkages of 3-O-substituted glucose units in 1,3-beta-glucans such as laminarin and curdlan, and also the 1,4-beta-linkages of 3-O-substituted beta-glucose in beta-glucans such as lichenin and 1,3-1, 4-beta-glucan from the cell walls of barley endosperm. The polysaccharide substrates (laminarin, curdlan and barley beta-glucan) were characterised using NMR spectroscopy. The reaction of LamR with its substrates was followed by recording one-dimensional and two-dimensional 1H-NMR and 13C-NMR spectra at suitable time intervals after addition of the enzyme. It is shown that hydrolysis occurs with retention of the anomeric configuration and that LamR performs transglycosylation to generate both 1, 3-beta-glycosidic and 1,4-beta glycosidic linkages. The transglycosylation results in, e.g. formation of the trisaccharide 4-O-glucosyl-laminaribiose from exclusively 1,3-beta-oligoglucosides. When barley 1,3-1,4-beta-glucan was incubated with LamR the beta-1, 4-linkages of 3-O-substituted beta-glycosyl residues were rapidly hydrolysed. Simultaneously de novo formation of 1,3-beta-glycosidic linkages was observed which, however, were cleaved during prolonged incubations. It is shown that a laminaribiosyl unit is the minimum requirement for formation of an enzyme-substrate complex and subsequent hydrolysis/transglycosylation.

The laminarinase from thermophilic eubacterium Rhodothermus marinus--conformation, stability, and identification of active site carboxylic residues by site-directed mutagenesis

A gene (lamR) encoding laminarinase (LamR) was cloned from the marine thermophilic eubacterium Rhodothermus marinus ITI278. The enzyme purified from recombinant Escherichia coli cells hydrolyses mixed 1,3-1,4-beta-glucans (lichenan, barley and oat beta-glucan) and 1,3-beta-homoglucans (laminarin, curdlan) by an endo type action pattern. The CD spectrum of laminarinase is characteristic for a protein with prevailing beta secondary-structural elements, and the fluorescence spectrum points to a surface localisation of the tryptophan residues. A half-transition concentration of 5.4 M guanidinium chloride was measured for the denaturant-induced unfolding of laminarinase monitoring changes of the ellipticity at 222 nm and the fluorescence. Substitution of acidic residues Glu129, Asp131 and Gln134, which are invariant in family 16 glycosyl hydrolases, caused a severe reduction of beta-glucan-hydrolysing activity suggesting their central role in enzymatic hydrolysis. Deletion of Met133 drastically reduced catalytic activity. Met133 is invariant in family 16 laminarinases but not present in the active-site region of bacterial 1,3-1,4-beta-glucanases which also belong to glycosyl hydrolase family 16. Replacement of Met133 by Ala, Cys or Trp did not affect activity against 1,3-1,4-beta-polyglucans and 1,3-beta-polyglucans, but in mutant Met133A the rate of hydrolysis of cellobiosyltriose (G1-4G1-3Gr) was increased about 10 times. Hydrolysis of 1,3-beta-oligosaccharides and 1,4-beta-oligosaccharides (DP 2-7) demonstrated the ability of the enzyme to cleave 1,3-beta-linkages and 1,4-beta-linkages in low-molecular-mass carbohydrates independent of the structure of neighbouring linkages. The laminarinase contains five or six subsites for substrate binding according to the action pattern deduced from hydrolysis of labelled and unlabelled curdlan oligosaccharides of different chain length.

Secular trends in blood pressure levels in Denmark 1964-1991

BACKGROUND

Hypertension is an essential risk factor for development of cardiovascular diseases. Prospective studies show a reduction in risk of myocardial infarction with reduction of blood pressure. In Denmark there was a decrease in ischaemic heart disease mortality during the period (1968-1992) with around 34% in 30-65 year old men and 30% in women.

OBJECTIVE

To assess the changes in casual blood pressure between 1964 and 1991 in seven cross-sectional population studies.

SETTING

Centre of Preventive Medicine, University of Copenhagen, DK-2600 Glostrup.

POPULATION

10359 subjects, equal numbers of men and women, age exactly 30, 40, 50 and 60 years drawn as random samples from a background population of 300000 inhabitants and surveyed in 1964-1974 and five cross-sectional studies 1976, 1978, 1982-1984, 1986-1987 and 1991.

METHODS

Blood pressure was measured according to WHO criteria by one technician in each survey. Alcohol consumption and physical activity were measured by a self-administered questionnaire. The weight and height were measured by standardized methods. Data on mortality from ischaemic heart disease were obtained from death certificates recorded by the National Board of Health.

RESULTS

Blood pressure increased with increasing age in both genders and was significantly higher in men than in women. Median blood pressure in 50 year old men in 1964 was 135/85 mmHg and in 1991 it was 123/79, whereas in women in 1964 it was 140/85, against 119/74 in 1991. The prevalence of hypertensives among 30 and 40 year olds declined throughout the period. The performance of blood pressure measurements, technical variation, examination programme, seasonal variation and inter-observer variation were potential bias sources and influenced blood pressure levels, but cannot be shown to be responsible for the declining trend in blood pressure and hypertension. Women became a little more physical active in leisure time and men less active. Women consumed less alcohol than men, but the amounts slightly increased by the end of the period. Body mass index >25 was seen less frequently in women than in men and this increased in men over the period. Sale of antihypertensive drugs increased in Denmark over the 1964-1991 period. There seems to be good agreement between the changes in blood pressure in the population and the decline in mortality from stroke and coronary heart disease in Denmark, which is influenced by other risk factors as well.

CONCLUSION

Blood pressure distributions have shifted towards lower values in 1964-1991. Prevalence of hypertension declined up to 1983. Risk factor changes as well as treatment for hypertension contribute to this.

Crystal structure of barley 1,3-1,4-beta-glucanase at 2.0-A resolution and comparison with Bacillus 1,3-1,4-beta-glucanase

Both plants and bacteria produce enzymes capable of degrading the mixed-linked beta-glucan of the endosperm cell walls of cereal grains. The enzymes share the specificity for beta-1,4 glycosyl bonds of O-3-substituted glucose units in linear polysaccharides and a similar cleavage mechanism but are unrelated in sequence and tertiary structure. The three-dimensional structure of the 1,3-1, 4-beta-glucanase isoenzyme EII from barley was determined from monoclinic crystals at a resolution of 2.0 A. The protein is folded into a betaalpha8 barrel structure as has been shown previously (Varghese, J. N., Garrett, T. P. J., Colman, P. M., Chen, L., Hoj, P. B., and Fincher, G. B. (1994) Proc. Natl. Acad. Sci. U.S.A. 91, 2785-2789) by diffraction analysis at lower resolution of tetragonal crystals. It contains one N-glycosylation site which is described in detail with the sugar moieties attached to residue Asn190. The geometry and hydration of the barley 1,3-1,4-beta-glucanase is analyzed; a model beta-glucan fragment is placed into the binding site by molecular dynamics simulation, and the beta-glucan binding grooves of the plant and bacterial enzymes are compared. Their active sites are shown to have a small number of common features in generally dissimilar geometries that serve to explain both the identical substrate specificity and the observed differences in inhibitor binding.

The glyoxysomal 3-ketoacyl-CoA thiolase precursor from Brassica napus has enzymatic activity when synthesized in Escherichia coli

Glyoxysomal 3-ketoacyl-CoA thiolase is the last enzyme in the beta-oxidation of fatty acids in plant glyoxysomes. A full-length cDNA of the glyoxysomal 3-ketoacyl-CoA thiolase from Brassica napus and a truncated version, lacking the N-terminal targeting signal were cloned in a T7 promoter-based vector. Both recombinant proteins were expressed in Escherichia coli and activity was measured. Full-length and truncated 3-ketoacyl-CoA thiolase have comparable activity in E. coli. Moreover, full-length 3-ketoacyl-CoA thiolase was purified from E. coli and N-terminal sequencing of the protein confirmed that the precursor form indeed is enzymatically active.

Mitral valve replacement with total preservation of native valve and subvalvular apparatus

BACKGROUND AND AIMS OF THE STUDY

Preservation of the mitral valve and subvalvular apparatus was introduced clinically in the early 1960s, but for two decades the technique for mitral valve replacement included excision of both leaflets and their attached chordae tendineae. Lately, emphasis has been replaced on retaining the mitral subvalvular apparatus during valve replacement because of its role in left ventricular function. Hence, during the past six years, when performing mitral valve replacement we have, when possible, preserved the valvular and sub-valvular mitral apparatus.

METHODS

Between January 1990 and November 1996, complete retention of all mitral tissue in connection with mitral valve replacement was performed in 58 patients (23 women and 35 men). Mean age was 63 years (range: 23 years to 77 years). Coronary bypass was a concomitant procedure in 19 patients; both the mitral and aortic valve was replaced in four cases. Calcified and/or stenotic valves were not a contraindication for the procedure; calcified plaques were removed. Adhesion between anterior and posterior leaflets was treated with sharp dissection. Valve and subvalvular tissue were preserved. The leaflets were reefed within the valve-sutures and compressed between the sewing ring and the native annulus when implanting the valve prosthesis. Chordal tension on the ventricle is thus maintained and the chordae pulled away from the valve effluent.

RESULTS

Six patients died in the postoperative period and three had transient neurological symptoms. In no patient was death or transient neurological symptoms a consequence of the retention of mitral leaflets with subvalvular apparatus.

CONCLUSIONS

We find the described technique to be useful not only in valve insufficiency but also in valve stenosis when preserving the mitral leaflets with sub-valvular apparatus during valve replacement. The technique is without procedure-related complications and prevents obstruction of left ventricular outflow tract.

Transgenic barley expressing a protein-engineered, thermostable (1,3-1,4)-beta-glucanase during germination

The codon usage of a hybrid bacterial gene encoding a thermostable (1,3-1,4)-beta-glucanase was modified to match that of the barley (1,3-1,4)-beta-glucanase isoenzyme EII gene. Both the modified and unmodified bacterial genes were fused to a DNA segment encoding the barley high-pI alpha-amylase signal peptide downstream of the barley (1,3-1,4)-beta-glucanase isoenzyme EII gene promoter. When introduced into barley aleurone protoplasts, the bacterial gene with adapted codon usage directed synthesis of heat stable (1,3-1,4)-beta-glucanase, whereas activity of the heterologous enzyme was not detectable when protoplasts were transfected with the unmodified gene. In a different expression plasmid, the codon modified bacterial gene was cloned downstream of the barley high-pI alpha-amylase gene promoter and signal peptide coding region. This expression cassette was introduced into immature barley embryos together with plasmids carrying the bar and the uidA genes. Green, fertile plants were regenerated and approximately 75% of grains harvested from primary transformants synthesized thermostable (1,3-1,4)-beta-glucanase during germination. All three trans genes were detected in 17 progenies from a homozygous T1 plant.

Transplanting two unique beta-glucanase catalytic activities into one multienzyme, which forms glucose

Endo cellulases of plant pathogenic erwinias degrade cellulose as well as the cellulosic domains of barley (1-3,1-4)-beta-glucan. Depolymerization of the latter substrate is mainly caused by (1-3,1-4)-beta-glucanases, which hydrolyze (1-4)-beta glycosidic linkages adjacent to (1-3)-beta linkages. To construct an enzyme for efficient degradation of barley (1-3,1-4)-beta-glucan, the sequence encoding the catalytic domain and interdomain linker of the cellulase from Erwinia carotovora subspecies atroseptica was fused to that for the heat stable Bacillus hybrid, H(A12-M) delta Y13 (1-3,1-4)-beta glucanase. The chimeric enzyme secreted from Escherichia coli cells did not remain covalently assembled as judged by SDS-PAGE. However, the glycosylated and intact enzyme (denoted CELGLU) is secreted from the yeast Pichia pastoris. CELGLU exhibits both cellulase and (1-3,1-4)-beta-glucanase catalytic activities, and was accordingly classified a true multienzyme. HPLC and NMR analyses revealed that among the products from CELGLU, di- and trimeric oligosaccharides were identical to those produced by the parental cellulase. Tetrameric oligosaccharides, derived from the (1-3,1-4)-beta-glucanase activity of CELGLU, were further degraded by the cellulase moiety to yield glucose and trimers. Compared with the parental enzymes, CELGLU exhibits substantially higher Vmax for degradation of both soluble cellulose and barley (1-3,1-4)-beta-glucan. These findings point to construction of multienzymes as an effective approach for engineering enzymes with novel characteristics.

Crystallization of barley (1-3,1-4)-beta-glucanase, isoenzyme II

The (1-3,1-4)-beta-glucanase from barley (Hordeum vulgare, cv Alexis) degrades mixed linked beta-glucan in the cell wall of the starchy endosperm. Isoenzyme II of the (1-3,1-4)-beta-glucanase forms large single crystals when a protein solution is equilibrated against 20% (w/w) polyethylene glycol 8000 at acidic pH using the hanging drop vapour diffusion method. The crystals diffract to better than 2 A resolution. They are monoclinic, space group P2(1), with cell dimensions a = 49.58 A, b = 82.99 A, c = 77.56 A and beta = 104.36 degrees. Two protein molecules are estimated to fill the asymmetric unit.

Crystallization of the hybrid Bacillus (1-3,1-4)-beta-glucanase H(A16-M)

The extremely thermostable hybrid Bacillus (1-3,1-4)-beta-glucanase H(A16-M) has been crystallized with polyethylene glycol by vapour diffusion. The single crystals diffract to a resolution of 2.2 A. The protein crystallizes in the orthorhombic space group P2(1)2(1)2(1) with a = 70.22(7) A, b = 72.56(1) A, c = 49.97(1) A, and has one molecule per asymmetric unit.

Hybrid Bacillus (1-3,1-4)-beta-glucanases: engineering thermostable enzymes by construction of hybrid genes

Hybrid (1-3,1-4)-beta-glucanase genes were constructed by extension of overlapping segments of the (1-3,1-4)-beta-glucanase genes from Bacillus amyloliquefaciens and B. macerans generated by the polymerase chain reaction (PCR). Four hybrid genes were expressed in Escherichia coli cells. The mature hybrid enzymes contain a 16, 36, 78, or 152 amino acid N-terminal sequence derived from B. amyloliquefaciens (1-3,1-4)-beta-glucanase followed by a C-terminal segment derived from B. macerans (1-3,1-4)-beta-glucanase. Biochemical characterization of parental and hybrid enzymes shows a significant increase in thermostability of three of the hybrid enzymes when exposed to an acidic environment thus combining two important enzyme characteristics within the same molecule. At pH 4.1, 85%-95% of the initial activity was retained after 1 h at 65 degrees C in contrast to 5% and 0% for the parental enzymes from B. amyloliquefaciens and B. macerans. After 60 min incubation at 70 degrees C, pH 6.0, the parental enzymes retained 5% or less of the initial activity whilst one of the hybrids still exhibited 90% of the initial activity. Of the parental enzymes B. macerans (1-3,1-4)-beta-glucanase had the lower specific activity while the hybrid enzymes exhibited specific activities that were 1.5- to 3-fold higher. These experimental results demonstrate that exchange of homologous gene segments from different species may be a useful technique for obtaining new and improved versions of biologically active proteins.

Hybrid bacillus endo-(1-3,1-4)-beta-glucanases: construction of recombinant genes and molecular properties of the gene products

Hybrid beta-glucanase genes were constructed by the reciprocal exchange of the two halves of the isolated beta-glucanase genes from Bacillus amyloliquefaciens and B. macerans. The beta-glucanase hybrid enzyme 1 (H1) contains the 107 amino-terminal residues of mature B. amyloliquefaciens beta-glucanase and the 107 carboxyl-terminal amino acid residues of B. macerans beta-glucanase. The reciprocal beta-glucanase hybrid enzyme 2 (H2) consists of the 105 amino-terminal residues from the B. macerans enzyme and the carboxyl-terminal 107 amino acids from B. amyloliquefaciens. The biochemical properties of the two hybrid enzymes differ significantly from each other as well as from both parental beta-glucanases. Hybrid beta-glucanase H1 exhibits increased thermostability in comparison to other beta-glucanases, especially in an acidic environment. This hybrid enzyme has maximum activity between pH 5.6 and 6.6, whereas the pH-optimum for enzymatic activity of B. amyloliquefaciens beta-glucanase was found to be at pH 6 to 7 and for B. macerans at pH 6.0 to 7.5. Hybrid enzyme 1 being more heat stable than both parental enzymes represents a case of intragenic heterosis. Hybrid beta-glucanase 2 (H2) was found to be more thermolabile than the naturally occurring beta-glucanases it was derived from and the pH-optimum for enzymatic activity was determined to be between pH 7 and pH 8.

Processing and secretion of barley (1-3,1-4)-beta-glucanase in yeast

DNA segments encoding signal peptides from mouse alpha-amylase, yeast acid phosphatase, and yeast invertase were fused in frame to a barley (1-3,1-4)-beta-glucanase cDNA gene and expressed in yeast cells under the control of the phosphoglycerate kinase gene promoter. Pure beta-glucanase is obtained by gel filtration of concentrated yeast cell supernatant. It was shown that the glucanase pre-protein was specifically processed and the mature protein efficiently secreted when the yeast invertase signal sequence directed secretion.

The structure of two distinct pancreatic amylase genes in mouse strain YBR

The amylase complex on mouse chromosome 3 encodes both salivary and pancreatic amylase. It appears that one active gene is present for salivary amylase, whereas pancreatic amylase in some strains is coded by at least 4, and perhaps by more than 10, genes. Strain YBR is different from other strains in that it produces twice as much salivary amylase. Pancreatic amylase in YBR is present as two different protein forms, A beta and B beta, the sum of which amounts to only one-third of that in, for instance, strain A/J. YBR chromosomal DNA was cloned in phage gamma, followed by restriction and heteroduplex analysis of recombinant phages carrying amylase genes. Among 32 phage isolates, 5 carried parts of the salivary amylase sequence. The remaining phage isolates contained pancreatic amylase-like sequences and represented three nonoverlapping genomic regions, i.e., one of 34 kb containing a complete gene, PAN-II beta; another of 41 kb with a complete but different gene, PAN-I beta, plus a truncated gene, PAN-psi 1; and finally, one of 23 kb with another truncated gene, PAN-psi 2. Parts of the amino acid sequence of A beta and B beta have previously been determined, and we report here the sequencing of a 4-kb DNA fragment from Pan-II beta which establishes that this gene codes for B beta.

Genetic variation in restriction patterns among mouse amylase gene complexes

The expression of pancreatic amylase in the mouse exhibits pronounced genetic variation. Congenic lines with various amylase complexes on a common C3H/As background have different numbers and forms of isoenzymes. The relative ratio of these isoenzymes may vary, as does the overall production of pancreatic amylase, which in some lines is three- to fourfold higher than in others. DNA from a number of lines was digested with endonucleases and hybridized to an amylase cDNA probe. The restriction patterns from inbred stocks and the corresponding congenic lines are identical, demonstrating that the majority of (if not all) amylase-like DNA sequences is found within the amylase complex. Congenic lines with specific amylase expression, for instance, in enzyme production, show different restriction patterns, whereas three lines with the same amylase phenotype have a uniform pattern. Most of the variation in amylase expression is represented among congenic lines derived from Danish mice. A comparison of such lines with others of remote geographic origin reveals that the restriction patterns of the "Danish" lines have by far the highest degree of resemblance. This observation seems to exclude major rearrangements within the amylase complex as the cause of the differences in enzyme expression, which instead are likely to be due to variation in regulatory elements associated with the active structural amylase genes in the complex.

Isolation and characterization of alpha-amylase messenger RNA from bank vole parotid glands. Evidence for two separate messenger RNAs coding for amylase and an amylase-related protein

Bank vole saliva contains two glycogen-precipitable proteins, both of which show affinity for the alpha-amylase inhibitor cycloheptaamylose. One of these proteins, amylase, has a molecular weight of 55,000, judged from dodecylsulphate/acrylamide gel electrophoresis. The other has an apparent molecular weight of 59,000 and has no amylase activity. We report here that tryptic peptide maps as well as amino-acid composition analyses indicate extensive homology between the two proteins. We have also isolated total poly(A)-containing mRNA from amylase-rich bank vole parotid glands. These mRNAs were translated in the presence of [35S]methionine in an mRNA-dependent cell-free translation system from rabbit reticulocyte lysate. The radioactive translation products were examined by dodecylsulphate/polyacrylamide gel electrophoresis. Two major translation products with apparent molecular weights of approximately 56,500 and 60,500, respectively, were further characterized by tryptic peptide analyses. Our data indicate that the 56,500-Mr product is the biosynthetic precursor of amylase, whereas the 60,500-Mr translation product is a precursor of the 59,000-Mr amylase-like protein. Both precursors appear to contain extra peptide material, presumably as amino-terminal 'pre' or 'signal' peptides, in analogy with that found for other precursors of secretory proteins. Thus, amylase and the 59,000-Mr protein, although very similar, are translated from two separate mRNAs. These two messengers sediment in a sucrose gradient at about 17-S, corresponding to lengths of about 1,800 nucleotides.