Search for Spin-Dependent Gravitational Interactions at Earth Range

Among the four fundamental forces, only gravity does not couple to particle spins according to the general theory of relativity. We test this principle by searching for an anomalous scalar coupling between the neutron spin and the Earth's gravity on the ground. We develop an atomic gas comagnetometer to measure the ratio of nuclear spin-precession frequencies between ^{129}Xe and ^{131}Xe, and search for a change of this ratio to the precision of 10^{-9} as the sensor is flipped in Earth's gravitational field. The null results of this search set an upper limit on the coupling energy between the neutron spin and the gravity on the ground at 5.3×10^{-22}  eV (95% confidence level), resulting in a 17-fold improvement over the previous limit. The results can also be used to constrain several other anomalous interactions. In particular, the limit on the coupling strength of axion-mediated monopole-dipole interactions at the range of Earth's radius is improved by a factor of 17.

Signal-processing electronics for stable and sensitive weak-field atomic vector magnetometers

We present the electronics developed for a sensitive and stable atomic vector magnetometer used in low-field detections. These electronics are required to be not only highly reliable and sophisticated for signal processing but also compact in size and low cost in resource consumption for the purpose of miniaturization. In addition, this magnetometer works with multiple modulations, where the interferences between harmonics of modulation fields often disturb the long-term measurements of the sensor. We work out a robust method to eliminate this problem by choosing the modulation frequencies with separations to match the minimum response points of the low-pass filters used in the demodulation processes. We validate the performance of the electronics and the frequency-selection scheme of the modulation fields with corresponding experimental results.

Search for Monopole-Dipole Interactions at the Submillimeter Range with a ^{129}Xe-^{131}Xe-Rb Comagnetometer

Monopole-dipole interactions involving scalar couplings between a spin and a massive particle violate both P and T symmetry, and can be mediated by axions. We use a ^{129}Xe-^{131}Xe-Rb atomic cell comagnetometer to measure the ratio of precession frequencies between the two xenon isotopes, and search for changes of the ratio correlated with the distance between the atomic cell and a nonmagnetic bismuth germanate crystal. A modulated Rb polarization scheme is used to suppress systematic effects by 2 orders of magnitude. The null results of this search improve the upper limit on the coupling strength g_{s}^{N}g_{p}^{n} over the interaction range 0.11-0.55 mm, and by a maximum improvement factor of 30 at 0.24 mm. The corresponding propagator mass range of this new excluded region covers 0.36-1.80 meV.

Halalkalibacterium roseum gen. nov., sp. nov., a new member of the family Balneolaceae isolated from soil

A Gram-stain-negative, non-motile, moderately halophilic and facultatively anaerobic bacterium, designated YR4-1T, was isolated from a saline-alkali and sorghum-planting soil sample collected in Dongying, Shandong Province, PR China. Growth occurred at 28–45 °C with the presence of 4.0–20.0 % (w/v) NaCl and pH 6.0–9.0. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that YR4-1T shared the highest similarity of 92.1–92.4 % with the valid published species of Aliifodinibius . The isolate formed a separate clade at the genus level in recently described family Balneolaceae . The draft genome of strain YR4-1T is 3.83 Mbp long with 44.0 mol% G+C content. The strain possesses several genes involved in the osmotic stress response mechanism and diverse metabolic pathways, probably for the living in saline environment. This may lead to a better understanding of the underrepresented Balneolaceae lineage. The major menaquinone was MK-7. The main polar lipid profile was composed of diphosphatidylglycerol, phosphatidylglycerol, phosphoglycolipids, aminophosphoglycolipid, one glycolipid, and four unidentified lipids. The predominant cellular fatty acids were iso-C15 : 0 (35.7 %) and anteiso-C15 : 0 (33.5 %). On the basis of its phenotypic, chemotaxonomic and phylogenetic features, strain YR4-1T represents a novel species of a new genus, for which the name Halalkalibacterium roseum gen. nov., sp. nov. is proposed. The type strain is YR4-1T (=CGMCC 1.17777T=KCTC 72795T).

Two new Polyangium species, P. aurulentum sp. nov. and P. jinanense sp. nov., isolated from a soil sample

Polyangium belongs to Polyangiaceae family of Myxococcales, a taxonomic group well-known for their extraordinary social lifestyle and diverse novel gene clusters of secondary metabolites. A yellow-golden strain, designated SDU3-1^T, and two rose pink strains, designated SDU13 and SDU14^T, were isolated from a soil sample. These three strains were aerobic, mesophilic, not salt-tolerant and were able to prey on living microorganisms. SDU13 and SDU14^T formed solitary sporangioles under starvation conditions, while SDU3-1^T had no fruiting body structures. They showed 95.9-97.0% (SDU3-1^T) or 98.7-98.9% (SDU13 and SDU14^T) 16S rRNA gene similarity with the type strains of Polyangium, but were phylogenetically separate from them based on the 16S rRNA gene and genome sequences. Their genomes were 12.3 Mbp (SDU3-1^T), 13.9 Mbp (SDU13) and 13.8 Mbp (SDU14^T) with the G + C content range of 68.3-69.4 mol%. The average nucleotide identity and DNA-DNA hybridization analyses of genomes further indicated that these three strains belonged to two new species in Polyangium. Their major fatty acids were C_18:1ω9c, C_16:0 and C_18:0. The polyphasic taxonomic characterization suggest that the three strains represent two novel species in the genus Polyangium, for which the names Polyangium aurulentum sp. nov. and Polyangium jinanense sp. nov. are proposed, and the type strains are SDU3-1^T (=CGMCC 1.16875^T = KCTC 72136^T) and SDU14^T (=CCTCC AB 2021123^T = KCTC 82625^T), respectively.

ParC, a New Partitioning Protein, Is Necessary for the Active Form of ParA From Myxococcus pMF1 Plasmid

The ParABS partitioning system, a main driver of DNA segregation in bacteria, employs two proteins, ParA and ParB, for plasmid partition. The pMF1 plasmid from Myxococcus fulvus 124B02 has a par operon encoding a small acidic protein, ParC, in addition to type I ParA and ParB homologs. Here, we show that expression of parC upstream of parA (as in the natural case), but not ectopic expression, is essential for the plasmid inheritance in Myxococcus cells. Co-expression of parC upstream of parA was determined to form a soluble ParC-ParA heterodimer at a 1:1 ratio, while individual expression of parA or co-expression of parA with ectopic parC formed insoluble ParA proteins. Purified ParA proteins alone had no ATPase activity and was easily dimerized, while mixing ParA with ParC formed the ParC-ParA heterodimer with the ATPase and polymerization activities. Fusing ParC and ParA also produced soluble proteins and some chimeras restored the ATPase activity and plasmid inheritance. The results highlight that proximal location of parC before parA is critical to realize the functions of ParA in the partition of Myxococcus plasmid pMF1 and shed light on a new mechanism to realize a protein function by two separate proteins.

The developmental regulator MtrA binds GlnR boxes and represses nitrogen metabolism genes in Streptomyces coelicolor

In Streptomyces, GlnR is an activator protein that activates nitrogen-assimilation genes under nitrogen-limiting conditions. However, less is known regarding the regulation of these genes under nitrogen-rich conditions. We determined that the developmental regulator MtrA represses nitrogen-assimilation genes in nitrogen-rich media and that it competes with GlnR for binding to GlnR boxes. The GlnR boxes upstream of multiple nitrogen genes, such as amtB, were confirmed as MtrA binding sites in vitro by electrophoretic mobility shift assays and in vivo by ChIP-qPCR analysis. Transcriptional analysis indicated that, on nutrient-rich medium, MtrA profoundly repressed expression of nitrogen-associated genes, indicating opposing roles for MtrA and GlnR in the control of nitrogen metabolism. Using in vitro and in vivo analysis, we also showed that glnR is itself a direct target of MtrA and that MtrA represses glnR transcription. We further demonstrated functional conservation of MtrA homologues in the recognition of GlnR boxes upstream of nitrogen genes from different actinobacterial species. As mtrA and glnR are widespread among actinomycetes, this mechanism of potential competitive control over nitrogen metabolism genes may be common in this group, adding a major new layer of complexity to the known regulatory network for nitrogen metabolism in Streptomyces and related species.

^{3}He-^{129}Xe Comagnetometery using ^{87}Rb Detection and Decoupling

We describe a ^{3}He-^{129}Xe comagnetometer using ^{87}Rb atoms for noble-gas spin polarization and detection. We use a train of ^{87}Rb π pulses and σ^{+}/σ^{-} optical pumping to realize a finite-field Rb magnetometer with suppression of spin-exchange relaxation. We suppress frequency shifts from polarized Rb by measuring the ^{3}He and ^{129}Xe spin precession frequencies in the dark, while applying π pulses along two directions to depolarize Rb atoms. The plane of the π pulses is rotated to suppress the Bloch-Siegert shifts for the nuclear spins. We measure the ratio of ^{3}He to ^{129}Xe spin precession frequencies with sufficient absolute accuracy to resolve Earth's rotation without changing the orientation of the comagnetometer. A frequency resolution of 7 nHz is achieved after integration for 8 h without evidence of significant drift.

A microfabricated optically-pumped magnetic gradiometer

We report on the development of a microfabricated atomic magnetic gradiometer based on optical spectroscopy of alkali atoms in the vapor phase. The gradiometer, which operates in the spin-exchange relaxation free regime, has a length of 60 mm and cross sectional diameter of 12 mm, and consists of two chip-scale atomic magnetometers which are interrogated by a common laser light. The sensor can measure differences in magnetic fields, over a 20 mm baseline, of 10 fT/[Formula: see text] at frequencies above 20 Hz. The maximum rejection of magnetic field noise is 1000 at 10 Hz. By use of a set of compensation coils wrapped around the sensor, we also measure the sensor sensitivity at several external bias field strengths up to 150 mG. This device is useful for applications that require both sensitive gradient field information and high common-mode noise cancellation.

New classes of systematic effects in gas spin comagnetometers

Atomic comagnetometers are widely used in precision measurements searching for spin interactions beyond the standard model. We describe a new (3)He-(129)Xe comagnetometer probed by Rb atoms and use it to identify two general classes of systematic effects in gas comagnetometers, one associated with diffusion in second-order magnetic-field gradients and another due to temperature gradients. We also develop and confirm experimentally a general and practical approach for calculating spin relaxation and frequency shifts due to arbitrary magnetic-field gradients.

New classes of systematic effects in gas spin comagnetometers

Atomic comagnetometers are widely used in precision measurements searching for spin interactions beyond the standard model. We describe a new (3)He-(129)Xe comagnetometer probed by Rb atoms and use it to identify two general classes of systematic effects in gas comagnetometers, one associated with diffusion in second-order magnetic-field gradients and another due to temperature gradients. We also develop and confirm experimentally a general and practical approach for calculating spin relaxation and frequency shifts due to arbitrary magnetic-field gradients.

Subfemtotesla scalar atomic magnetometry using multipass cells

Scalar atomic magnetometers have many attractive features but their sensitivity has been relatively poor. We describe a Rb scalar gradiometer using two multipass optical cells. We use a pump-probe measurement scheme to suppress spin-exchange relaxation and two probe pulses to find the spin precession zero crossing times with a resolution of 1 psec. We realize a magnetic field sensitivity of 0.54 fT/Hz(1/2), which improves by an order of magnitude the best scalar magnetometer sensitivity and exceeds, for example, the quantum limit set by the spin-exchange collisions for a scalar magnetometer with the same measurement volume operating in a continuous regime.

Sensitivity test of a blue-detuned dipole trap designed for parity non-conservation measurements in Fr

A dynamic blue-detuned optical dipole trap with stable (87)Rb atoms produces a differential ac Stark shift of 18 Hz in the ground state hyperfine transition, and it preserves the ground state hyperfine superpositions for a long coherence time of 180 ms. The trapped atoms undergoing microwave Rabi oscillations are sensitive to a small signal, artificially generated with a second microwave source, phase locked to the first allowing a simple and effective method for determining signal-to-noise ratio limits through interference techniques. This provides an excellent means of calibrating sensitivity in experiments such as our ongoing Fr parity non-conservation measurement.

Role of Escherichia coli strain subgroups, integrons, and integron-associated gene cassettes in dissemination of antimicrobial resistance in aquatic environments of Jinan, China

Aquatic environments are known reservoirs of antibiotic-resistant bacteria, but little information is known about the role of Escherichia coli strain subgroups, integrons, and integron-associated gene cassettes in the prevalence of antimicrobial resistance. To address these knowledge gaps, the diversity and distribution of drug-resistant E. coli strains and their integrons in hospital wastewater (HWW) and XiaoQing River water (XQRW) in Jinan, China were compared. Phylogenetic assays showed that the isolates were distributed in every E. coli subgroup. The prevalence of antibiotic resistance in each E. coli subgroup from HWW was higher than in subgroups from XQRW, except for phylogenetic subgroup A(0). Classes 1 and 2 integrons were found in 327 strains (78.2% of the total 418 isolates) with a prevalence of 85.6% among the 209 isolates from HWW. Among 15 gene cassette arrays, dfrA17-aadA5 and dfrA12-orfF-aadA2 were the most prevalent. The prevalence of drug-resistance gene cassettes and diversity of arrays further proved that integrons were important contributors to the widespread occurrence of antibiotic resistance in E. coli among Jinan aquatic environments.

Dissection of the functional domains of an archaeal Holliday junction helicase

Helicases and nucleases form complexes that play very important roles in DNA repair pathways some of which interact with each other at Holliday junctions. In this study, we present in vitro and in vivo analysis of Hjm and its interaction with Hjc in Sulfolobus. In vitro studies employed Hjm from the hyperthermophilic archaeon Sulfolobus tokodaii (StoHjm) and its truncated derivatives, and characterization of the StoHjm proteins revealed that the N-terminal module (residues 1-431) alone was capable of ATP hydrolysis and DNA binding, while the C-terminal one (residues 415-704) was responsible for regulating the helicase activity. The region involved in StoHjm-StoHjc (Hjc from S. tokodaii) interaction was identified as part of domain II, domain III (Winged Helix motif), and domain IV (residues 366-645) for StoHjm. We present evidence supporting that StoHjc regulates the helicase activity of StoHjm by inducing conformation change of the enzyme. Furthermore, StoHjm is able to prevent the formation of Hjc/HJ high complex, suggesting a regulation mechanism of Hjm to the activity of Hjc. We show that Hjm is essential for cell viability using recently developed genetic system and mutant propagation assay, suggesting that Hjm/Hjc mediated resolution of stalled replication forks is of crucial importance in archaea. A tentative pathway with which Hjm/Hjc interaction could have occurred at stalled replication forks is discussed.

The carboxyl terminal of the archaeal nuclease NurA is involved in the interaction with single-stranded DNA-binding protein and dimer formation

The nuclease NurA is present in all known thermophilic archaea and has been implicated to facilitate efficient DNA double-strand break end processing in Mre11/Rad50-mediated homologous recombinational repair. To understand the structural and functional relationship of this enzyme, we constructed five site-directed mutants of NurA from Sulfolobus tokodaii (StoNurA), D56A, E114A, D131A, Y291A, and H299A, at the conserved motifs, and four terminal deletion mutants, StoNurAΔN (19-331), StoNurAΔNΔC (19-303), StoNurAΔC (1-281), and StoNurAΔC (1-303), and characterized the proteins biochemically. We found that mutation at the acidic residue, D56, E114, D131, or at the basic residue, H299, abolishes the nuclease activity, while mutation at the aromatic residue Y291 only impairs the activity. Interestingly, by chemical cross-linking assay, we found that the mutant Y291A is unable to form stable dimer. Additionally, we demonstrated that deletion of the C-terminal amino acid residues 304-331 of StoNurA results in loss of the physical and functional interaction with the single-stranded DNA-binding protein (StoSSB). These results established that the C-terminal conserved aromatic residue Y291 is involved in dimer formation and the C-terminal residues 304-331 of NurA are involved in the interaction with single-stranded DNA-binding protein.

Sitagliptin 100 mg daily effect on DPP-4 inhibition and compound-specific glycemic improvement

OBJECTIVE

In clinical trials, the degree of glucose lowering with sitagliptin has been correlated with the magnitude of dipeptidyl peptidase-4 (DPP-4) inhibition over 24 h. Previous studies evaluating sitagliptin doses ranging from 25 to 200 mg/day demonstrated that the daily dose of 100 mg provided maximal glucose-lowering efficacy for this compound in patients with type 2 diabetes. However, sitagliptin 200 mg once daily provided numerically greater percent plasma DPP-4 inhibition compared with 100 mg once daily. The purpose of this study was to evaluate whether sitagliptin 200 mg once daily provides greater improvement in glycemic efficacy as assessed by weighted mean glucose (WMG) over 24 h relative to sitagliptin 100 mg once daily and to relate the percent DPP-4 inhibition achieved with these doses to any between-treatment differences in glycemic efficacy.

METHODS

In a double-blind crossover study, patients with type 2 diabetes (fasting plasma glucose [FPG] 130-250 mg/dL) were randomized to one of six treatment sequences over three treatment periods (placebo, sitagliptin 100 mg once daily, or sitagliptin 200 mg once daily). Each of the treatment periods was 7 days in duration, with 28-day washout periods between treatments. After each treatment period, patients underwent blood sampling at various time points over 24 h to determine 24-h WMG. Plasma DPP-4 activity was assessed at trough, 24 h following dosing on day 7; percent DPP-4 inhibition was corrected for sample assay dilution.

RESULTS

The 103 randomized patients had a baseline mean FPG of 172 mg/dL. Following a planned interim analysis, the study was stopped because the 24-h WMG values were not different between the sitagliptin doses. Furthermore, a significant carryover effect across periods was observed for FPG; thus, efficacy results from period 1 are presented herein. The 24-h WMG values were significantly (p < 0.01) lower with sitagliptin relative to placebo, but the difference between sitagliptin doses was not significant (p = 0.365). Corrected percent plasma DPP-4 inhibition at trough was not significantly (p = 0.791) different with sitagliptin 200 mg (LS mean [95% CI] 96.9% [90.0, 100.0]) compared with sitagliptin 100 mg (95.6% [88.4, 100.0]). The early termination and the carryover effect described above are limitations to this study.

CONCLUSION

Across sitagliptin doses in this study, the similarity of the 24-h WMG concentrations and the similarity of the corrected DPP-4 inhibition values support prior findings that the maximal glucose-lowering efficacy of sitagliptin is achieved with once-daily dosing of 100 mg. Clinicaltrials.gov: NCT00541229.

Residue Tyr224 is critical for the thermostability of Geobacillus sp. RD-2 lipase

A thermophilic lipase (lipGRD) from Geobacillus sp. RD-2, isolated from a hot spring in Yunnan, China, was cloned and over-expressed in Escherichia coli. The function of the conserved residue, Tyr224, near the presumed temperature switch site was analyzed by site-directed saturation mutagenesis. The activity of the wild type lipGRD was optimal at 55 degrees C and pH 7.5, but that from mutant Y224C was optimally active at 35 degrees C, whereas Y224P lipase was optimally active at 65 degrees C. Furthermore, the latter lipase retained 60% of its activity after incubation at 65 degrees C for 5 h. The conserved residue Tyr224, which is close to the lid helix, is the key amino acid residue determining the thermostability of the thermostable lipase.

Safety and efficacy of sitagliptin in patients with type 2 diabetes and chronic renal insufficiency

OBJECTIVE

To assess the safety of sitagliptin in patients with type 2 diabetes and moderate [creatinine clearance (CrCl) > or =30 to <50 ml/min] or severe renal insufficiency [CrCl <30 ml/min including patients with end-stage renal disease (ESRD) on dialysis]. The efficacy of sitagliptin in this patient population was also assessed.

METHODS

In a 54-week, randomized, double-blind, parallel-group study, patients with baseline glycosylated haemoglobin A(1c) (HbA(1c)) values of 6.5-10% were allocated (2:1) to sitagliptin (for 54 weeks) or the sequence of placebo (for 12 weeks) followed by active treatment with glipizide (for 42 weeks). To achieve plasma concentrations similar to those observed in patients with normal renal function treated with 100 mg sitagliptin once daily, patients with moderate renal insufficiency were allocated to receive sitagliptin 50 mg once daily and patients with severe renal insufficiency to receive 25 mg once daily. Glipizide treatment was initiated at 2.5 or 5 mg/day and uptitrated to a maximum of 20 mg/day.

RESULTS

Patients (N = 91) with a mean baseline HbA(1c) value of 7.7% (range: 6.2-10.3%) were randomized to sitagliptin (n = 65) or placebo (n = 26). After 12 weeks, the mean change [95% confidence interval (CI)] from baseline in HbA(1c) was -0.6% (-0.8, -0.4) in the sitagliptin group compared with -0.2% (-0.4, 0.1) in the placebo group [between-group difference (95% CI) = -0.4% (-0.7, -0.1)]. At 54 weeks, patients continuously treated with sitagliptin had a mean change (95% CI) from baseline in HbA(1c) of -0.7% (-0.9, -0.4). The overall incidence of adverse experiences was generally similar between groups. Between-group differences in incidences of specific clinical adverse experiences were generally small; however, the proportion of patients for whom hypoglycaemia was reported was lower in the sitagliptin group (4.6%) compared with the placebo/glipizide group (23.1%). Consistent with the high mortality risk in this patient population, there were six deaths during this 54-week study [5 of 65 patients (7.7%) in the sitagliptin group and 1 of 26 patients (3.8%) in the placebo/glipizide group]; no death was considered by the investigator to be drug related. The overall incidences of drug-related and serious adverse experiences and discontinuations because of adverse experiences were generally similar between groups.

CONCLUSIONS

In this study, sitagliptin was generally well tolerated and provided effective glycaemic control in patients with type 2 diabetes and moderate to severe renal insufficiency, including patients with ESRD on dialysis.

Archaeal DNA helicase HerA interacts with Mre11 homologue and unwinds blunt-ended double-stranded DNA and recombination intermediates

HerA is a novel family DNA helicases that exist ubiquitously in thermophilic archaea. The genes are linked to homologues of eukaryotic recombination and repair proteins Mre11 and Rad50 in some of the genomes. However, the relationship between HerA and the related proteins is unclear. In this study, a homologue from the hyperthermophilic archaeon Sulfolobus tokodaii (StoHerA) was characterized and physical and functional interactions between StoHerA and StoMre11 (Mre11 from S. tokodaii) were studied. It was found that StoHerA was able to unwind blunt-ended double-stranded DNA (dsDNA), although with lower efficiency. StoHerA was also able to unwind Holliday junction, splayed-arm DNA, as well as 5'- or 3'-overhang with high efficiency. Pull-down and yeast two-hybrid analyses revealed that StoHerA interacted with StoMre11 physically. The helicase activity of StoHerA was stimulated by StoMre11, indicating a functional role of this interaction. In addition, site-directed mutagenesis of StoHerA was performed to analyze functions of conserved residues of StoHerA. Interestingly, mutation of E355 to alanine in Walker B resulted in not only loss of ATPase and DNA helicase activities, but also dsDNA-binding ability, indicating that this residue is involved in the coupling of ATP hydrolysis, dsDNA-binding, and helicase activities.

[Cloning, expression and radiation inducibility of RadA from the hyperthermophilic archaeon Sulfolobus tokodaii]

RecA/Rad51/RadA recombinases are important recombination proteins with conserved functions. Studies on the enzymes have shown that members of RecA/Rad51/RadA family from bacteria, eukaryota, methanogens and halophilic archaea have UV inducibility. However, the UV inducibility of RadA homologues from hyperthermophilic archaea is controversial. We analyzed the UV inducibility of Sulfolobus tokodaii RadA by RT-PCR and immune assays. Comparing with the mock, the transcription and expression of the radA increased 2 and 1.5 folds respectively after UV irradiation at 100 J/m2, or 3 and 1 fold at 200 J/m2. These results demonstrated that S. tokodaii RadA could be induced after UV treatment. In addition, proteome induction analysis proved that there existed a DNA damage induction response in S. tokodaii, which further supported RadA inductility in this hyperthermophilic archaeon.

A unique highly thermostable 2-phosphoglycerate forming glycerate kinase from the hyperthermophilic archaeon Pyrococcus horikoshii: gene cloning, expression and characterization

A glycerate kinase (GK) gene (PH0495) from the hyperthermophilic archaeon Pyrococcus horikoshii, was cloned and expressed in Escherichia coli. The recombinant protein was purified to homogeneity by affinity chromatography and ion exchange chromatography. The enzyme was likely a homodimer based on SDS-PAGE (47 kDa) and gel filtration chromatography (100 kDa) analysis. A radioisotope-labeling examination method was initially used for the enzymatic activity detection, and the enzyme (GK(ph)) was found to catalyze the formation of 2-phosphoglycerate using D: -glycerate as the substrate. The enzyme exhibited unique phosphoryl donor specificity with maximal activity towards pyrophosphate. The temperature and pH optima of the enzyme were 45 degrees C and 7.0, respectively, and about half of the maximal activity remained at 100 degrees C. The enzyme was highly thermostable with almost no loss of activity at 90 degrees C for 12 h. Based on sequence alignment and structural comparison it was assigned to group I of the trichotomy of GKs.

Efficacy and safety of the dipeptidyl peptidase-4 inhibitor, sitagliptin, compared with the sulfonylurea, glipizide, in patients with type 2 diabetes inadequately controlled on metformin alone: a randomized, double-blind, non-inferiority trial

AIM

To compare the efficacy and safety of sitagliptin vs. glipizide in patients with type 2 diabetes and inadequate glycaemic control [haemoglobin A(1c) (HbA(1c)) > or = 6.5 and < or = 10%] on metformin monotherapy.

METHODS

After a metformin dose titration/stabilization period (> or = 1500 mg/day), 1172 patients were randomized to the addition of sitagliptin 100 mg q.d. (N = 588) or glipizide 5 mg/day (uptitrated to a potential maximum 20 mg/day) (N = 584) for 52 weeks. The primary analysis assessed whether sitagliptin was non-inferior to glipizide regarding HbA(1c) changes from baseline at Week 52 using a per-protocol approach.

RESULTS

From a mean baseline of 7.5%, HbA(1c) changes from baseline were -0.67% at Week 52 in both groups, confirming non-inferiority. The proportions achieving an HbA(1c) < 7% were 63% (sitagliptin) and 59% (glipizide). Fasting plasma glucose changes from baseline were -0.56 mmol/l (-10.0 mg/dl) and -0.42 mmol/l (-7.5 mg/dl) for sitagliptin and glipizide, respectively. The proportion of patients experiencing hypoglycaemia episodes was significantly (p < 0.001) higher with glipizide (32%) than with sitagliptin (5%), with 657 events in glipizide-treated patients compared with 50 events in sitagliptin-treated patients. Sitagliptin led to weight loss (change from baseline =-1.5 kg) compared with weight gain (+1.1 kg) with glipizide [between-treatment difference (95% confidence interval) =-2.5 kg (-3.1, -2.0); p < 0.001].

CONCLUSIONS

In this study, the addition of sitagliptin compared with glipizide provided similar HbA(1c)-lowering efficacy over 52 weeks in patients on ongoing metformin therapy. Sitagliptin was generally well tolerated, with a lower risk of hypoglycaemia relative to glipizide and with weight loss compared with weight gain with glipizide.

Efficacy and safety of the dipeptidyl peptidase-4 inhibitor, sitagliptin, compared with the sulfonylurea, glipizide, in patients with type 2 diabetes inadequately controlled on metformin alone: a randomized, double-blind, non-inferiority trial

AIM

To compare the efficacy and safety of sitagliptin vs. glipizide in patients with type 2 diabetes and inadequate glycaemic control [haemoglobin A(1c) (HbA(1c)) > or = 6.5 and < or = 10%] on metformin monotherapy.

METHODS

After a metformin dose titration/stabilization period (> or = 1500 mg/day), 1172 patients were randomized to the addition of sitagliptin 100 mg q.d. (N = 588) or glipizide 5 mg/day (uptitrated to a potential maximum 20 mg/day) (N = 584) for 52 weeks. The primary analysis assessed whether sitagliptin was non-inferior to glipizide regarding HbA(1c) changes from baseline at Week 52 using a per-protocol approach.

RESULTS

From a mean baseline of 7.5%, HbA(1c) changes from baseline were -0.67% at Week 52 in both groups, confirming non-inferiority. The proportions achieving an HbA(1c) < 7% were 63% (sitagliptin) and 59% (glipizide). Fasting plasma glucose changes from baseline were -0.56 mmol/l (-10.0 mg/dl) and -0.42 mmol/l (-7.5 mg/dl) for sitagliptin and glipizide, respectively. The proportion of patients experiencing hypoglycaemia episodes was significantly (p < 0.001) higher with glipizide (32%) than with sitagliptin (5%), with 657 events in glipizide-treated patients compared with 50 events in sitagliptin-treated patients. Sitagliptin led to weight loss (change from baseline =-1.5 kg) compared with weight gain (+1.1 kg) with glipizide [between-treatment difference (95% confidence interval) =-2.5 kg (-3.1, -2.0); p < 0.001].

CONCLUSIONS

In this study, the addition of sitagliptin compared with glipizide provided similar HbA(1c)-lowering efficacy over 52 weeks in patients on ongoing metformin therapy. Sitagliptin was generally well tolerated, with a lower risk of hypoglycaemia relative to glipizide and with weight loss compared with weight gain with glipizide.

Cloning, expression and characterization of a thermostable exo-beta-D-glucosaminidase from the hyperthermophilic archaeon Pyrococcus horikoshii

An exo-beta-D-glucosaminidase gene (PH0511) was cloned from the hyperthermophilic archaeon, Pyrococcus horikoshii, and expressed in Escherichia coli. The purified protein showed a strong exo-beta-D: -glucosaminidase activity by TLC analysis. DTT (50 mM) had little effect on its homodimeric structure during SDS-PAGE. The enzyme was optimally active at 90 degrees C (over 20 min) and pH 6. It had a half-life of 9 h at 90 degrees C and is the most thermostable glucosaminidase described up to now. The activity was not inhibited by ethanol, 2-propanol, DMSO, PEG-400, denaturing agents SDS (5%, w/v), urea, guanidine hydrochloride (5 M) and Mg(2+), Mn(2+), Co(2+), Ca(2+), Sr(2+), Ni(2+) (at up to 10 mM).

Proteomic analysis of Deinococcus radiodurans recovering from gamma-irradiation

In order to reveal the mechanisms of the extreme radioresistance and DNA repair in Deinococcus radiodurans, we examined proteome changes in a wild-type strain following gamma-irradiation using two-dimensional polyacrylamide gel electrophoresis and Silver-staining. The expression levels of 26 protein spots showed significant changes under radiation stress. Of these spots, 21 were identified with peptide mass fingerprinting using matrix-assisted laser desorption/ionization-time of flight mass spectrometry after tryptic in-gel digestion. These proteins exhibited various cellular functions, including (i) translation; (ii) transcription; (iii) signal transduction; (iv) post-translational modification, protein turnover, chaperones; (v) carbohydrate transport and metabolism; (vi) energy production and conversion; (vii) nucleotide transport and metabolism; (viii) inorganic ion transport and metabolism; (ix) DNA replication, recombination and repair; and (x) yet unknown. Most of the proteins have not previously been reported to be relevant to radioresistance.

A randomized clinical trial of valacyclovir in multiple sclerosis

OBJECTIVE

The human Herpesvirus type-6 (HHV-6) has been implicated in multiple sclerosis (MS). Valacyclovir is an antiviral agent with an excellent safety profile. A two-year placebo-controlled, double-blind study was conducted to (1) ascertain if high-dose, prolonged treatment with valacyclovir would be safe and (2) observe if valacyclovir would delay the progression of MS clinically or by magnetic resonance imaging (MRI).

DESIGN/METHODS

Fifty-eight patients were stratified as to severity and randomly assigned to receive valacyclovir (3000 mg/day) or placebo for a period of two years. Patients were followed clinically over the two-year period by means of the Expanded Disability Status Scale (EDSS), the Ambulation Index (AI) and brain MRI scans. Patients underwent routine lab studies every three months. Patients continued on the medication for two years unless they had a sustained progression or repeated exacerbations.

RESULTS

No patient discontinued the study due to side effects or toxicity. In Relative Ranking of Progression, time to first attack, attack rate, and time to withdrawal there were trends (but not statistically significant) toward drug effect over placebo in the Severe clinical category. MRI evaluation showed no significant drug effect.

CONCLUSIONS

Although not statistically significant, positive trends were detected for acyclovir by clinical measures, but not by MRI.

Dual negative regulatory mechanisms of RecX on RecA functions in radiation resistance, DNA recombination and consequent genome instability in Deinococcus radiodurans

RecA protein plays a central role in homologous recombination and DNA repair. RecX, a gene directly downstream in Escherichia coli and some other bacterial species, down regulates it. However, the precise mechanism of regulation of RecA by RecX is not known. In order to study the function of RecX in the highly radioresistant bacterium Deinococcus radiodurans, null and overexpression strains were constructed. Our data demonstrates that RecX represses radiation resistance, DNA recombination and consequent genome instability in the stationary phase bacteria. Further biochemical analyses reveal that RecX not only down regulates recA transcription, but also directly inhibits RecA activities in vitro. These data suggests a dual negative regulatory control of RecX on RecA functions in D. radiodurans.

RecX is involved in antioxidant mechanisms of the radioresistant bacteriumDeinococcus radiodurans

Deinococcus radiodurans shows remarkable resistance to reactive oxygen species (ROS), generated by irradiation. Disruption of recX (dr1310) in D. radiodurans using targeted mutagenesis method enhanced its ROS scavenging activity, and recX overexpression in this bacterium repressed its antioxidant activity significantly. Further analyses on catalase and superoxide dismutase, two important antioxidant proteins in cells, showed that RecX could repress the induction of antioxidant enzymes, revealing that it negatively regulates the ROS scavenging activity in D. radiodurans.

LexA Analog (dra0074) Is a Regulatory Protein That Is Irrelevant to recA Induction

The protein DRA0074 is suggested to be another LexA in Deinococcus radiodurans, having similar motifs and RecA-mediated cleavage activity to D. radiodurans LexA (dra0344). However, its function has not been studied. We disrupted the gene dra0074 and measured its effect on RecA induction using fusion translation, immunoblot, and proteomic analysis. Results showed that the product of gene dra0074 is not involved in RecA induction, but is a regulator of other metabolisms in D. radiodurans.

Expression of Deinococcus radiodurans PprI enhances the radioresistance of Escherichia coli

PprI, a newly identified gene switch responsible for extreme radioresistance of Deinococcus radiodurans, plays a central regulatory role in multiple DNA damage repair and protection pathways in response to radiation stress [Biochem. Biophy. Res. Commun. 306 (2003) 354]. To evaluate whether PprI also functions in the radioresistance in other organisms, D. radiodurans PprI protein (Deira-PprI) was expressed in Escherichia coli. The complemented E. coli strain showed an increase of approximately 1.6-fold radioresistance with a high dose of gamma irradiation. Immunoblotting assays showed that the expression of Deira-PprI in E. coli resulted in a significant increase in RecA protein expression following high dose ionizing radiation. The expression of Deira-PprI protein also significantly enhanced the scavenging ability of free radicals by inducing the enzymatic activity of KatG. These results indicate that exogenous expression of Deira-PprI promotes DNA repair and protection pathways and enhances the radioresistance of E. coli.

Chemiluminescence assay for reactive oxygen species scavenging activities and inhibition on oxidative damage of DNA inDeinococcus radiodurans

Free radical scavenging effects of the cellular protein extracts from two strains of Deinococcus radiodurans and Escherichia coli against O2-, H2O2 and *OH were investigated by chemiluminescence (CL) methods. The cellular protein extracts of D. radiodurans R1 and KD8301 showed higher scavenging effects on O2- than that of E. coli. D. radiodurans R1 and KD8301 also strongly scavenged H2O2 with an EC50 (50% effective concentration) of 0.12 and 0.2 mg/mL, respectively, compared to that of E. coli (EC50 = 3.56 mg/mL). The two strains of D. radiodurans were effective in scavenging *OH generated by the Fenton reaction, with EC50 of 0.059 and 0.1 mg/mL, respectively, compared to that of E. coli (EC50 > 1 mg/mL). Results from the chemiluminescence assay of *OH-induced DNA damage and the plasmid pUC18 DNA double-strand break (DSB) model in vitro showed that D. radiodurans had remarkably inhibitory effect on the *OH-induced oxidative damage of DNA. The scavenging effects of D. radiodurans on reactive oxygen species (ROS) played an important role in the response to oxidation stress and preventing against DNA oxidative damage, and may be attributed to intracellular scavenging proteins, including superoxide dismutase (SOD) and catalase.

Mechanistic studies of cyclohexanone monooxygenase: chemical properties of intermediates involved in catalysis

Cyclohexanone monooxygenase (CHMO), a bacterial flavoenzyme, carries out an oxygen insertion reaction on cyclohexanone to form a seven-membered cyclic product, epsilon-caprolactone. The reaction catalyzed involves the four-electron reduction of O2 at the expense of a two-electron oxidation of NADPH and a two-electron oxidation of cyclohexanone to form epsilon-caprolactone. Previous studies suggested the participation of either a flavin C4a-hydroperoxide or a flavin C4a-peroxide intermediate during the enzymatic catalysis [Ryerson, C. C., Ballou, D. P., and Walsh, C. (1982) Biochemistry 21, 2644-2655]. However, there was no kinetic or spectral evidence to distinguish between these two possibilities. In the present work we used double-mixing stopped-flow techniques to show that the C4a-flavin-oxygen adduct, which is formed rapidly from the reaction of oxygen with reduced enzyme in the presence of NADP, can exist in two states. When the reaction is carried out at pH 7.2, the first intermediate is a flavin C4a-peroxide with maximum absorbance at 366 nm; this intermediate becomes protonated at about 3 s(-1) to form what is believed to be the flavin C4a-hydroperoxide with maximum absorbance at 383 nm. These two intermediates can be interconverted by altering the pH, with a pK(a) of 8.4. Thus, at pH 9.0 the flavin C4a-peroxide persists mainly in the deprotonated form. Further kinetic studies also demonstrated that only the flavin C4a-peroxide intermediate could oxygenate the substrate, cyclohexanone. The requirement in catalysis of the deprotonated flavin C4a-peroxide, a nucleophile, is consistent with a Baeyer-Villiger rearrangement mechanism for the enzymatic oxygenation of cyclohexanone. In the course of these studies, the Kd for cyclohexanone to the C4a-peroxyflavin form of CHMO was determined to be approximately 1 microM. The rate-determining step in catalysis was shown to be the release of NADP from the oxidized enzyme.

MnII is not a productive substrate for wild-type or recombinant lignin peroxidase isozyme H2

The glyceraldehyde-3-phosphate dehydrogenase (gpd) gene promoter was used to drive the homologous expression of the lignin peroxidase (LiP) isozyme H2 gene in primary metabolic cultures of Phanerochaete chrysosporium. The molecular mass, pI, and optical absorption spectra of purified recombinant LiPH2 (rLiPH2) were essentially identical to those of wild-type LiPH2 (wtLiPH2). wtLiPH2 was prepared by growing cells in the absence of MnII, conditions under which P. chrysosporium manganese peroxidase (MnP) is not expressed, ensuring that wtLiPH2 was not contaminated with MnP. The kinetics of veratryl alcohol (VA) oxidation were essentially identical for rLiPH2 and wtLiPH2. The rLiPH2, wtLiPH2, and wild-type LiP isozyme H8 (wt-LiPH8) enzymes were used to reexamine previous claims that LiPH2 can oxidize Mn" at a rate sufficient to promote catalytic turnover of the enzyme. Our results demonstrate that rLiPH2, wtLiPH2, and LiPH8 do not turn over under steady-state conditions, when MnII is the sole reducing substrate. Furthermore, transient-state kinetic analyses show that the reduction rate of the catalytic intermediate, LiP compound I, by VA was at least 2 x 10(3)-fold higher than the rate of reduction in the presence of MnII. No reduction of LiP compound II was observed in the presence of MnII. In contrast to previous claims, these data strongly suggest that MnII is not a productive substrate for LiPH2 or LiPH8.

Oxidative polymerization of ribonuclease A by lignin peroxidase from Phanerochaete chrysosporium. Role of veratryl alcohol in polymer oxidation

The mechanism of lignin peroxidase (LiP) was examined using bovine pancreatic ribonuclease A (RNase) as a polymeric lignin model substrate. SDS/PAGE analysis demonstrates that an RNase dimer is the major product of the LiP-catalyzed oxidation of this protein. Fluorescence spectroscopy and amino acid analyses indicate that RNase dimer formation is due to the LiP-catalyzed oxidation of Tyr residues to Tyr radicals, followed by intermolecular radical coupling. The LiP-catalyzed polymerization of RNase in strictly dependent on the presence of veratryl alcohol (VA). In the presence of 100 microM H2O2, relatively low concentrations of RNase and VA, together but not individually, can protect LiP from H2O2 inactivation. The presence of RNase strongly inhibits VA oxidation to veratraldehyde by LiP; whereas the presence of VA does not inhibit RNase oxidation by LiP. Stopped-flow and rapid-scan spectroscopy demonstrate that the reduction of LiP compound I (LiPI) to the native enzyme by RNase occurs via two single-electron steps. At pH 3.0, the reduction of LiPI by RNase obeys second-order kinetics with a rate constant of 4.7 x 10(4) M-1.s-1, compared to the second-order VA oxidation rate constant of 3.7 x 10(5) M-1.s-1. The reduction of LiP compound II (LiPII) by RNase also follows second-order kinetics with a rate constant of 1.1 x 10(4) M-1.s-1, compared to the first-order rate constant for LiPII reduction by VA. When the reductions of LiPI and LiPIi are conducted in the presence of both VA and RNase, the rate constants are essentially identical to those obtained with VA alone. These results suggest that VA is oxidized by LiP to its cation radical which, while still in its binding site, oxidizes RNase.

2-Chloro-1,4-dimethoxybenzene cation radical: formation and role in the lignin peroxidase oxidation of anisyl alcohol

2-Chloro-1,4-dimethoxybenzene (2Cl-1,4-DMB) oxidation by lignin peroxidase (LiP) proceeds via the formation of the 2Cl-1,4-DMB cation radical as indicated by ESR and UV/vis spectroscopy. The products of the LiP-catalyzed oxidation of 2Cl-1,4-DMB were identified as 2-chloro-1,4-benzoquinone and the dimers dichlorotetramethoxybiphenyl and chloro(chlorodimethoxyphenyl)benzoquinone. The addition of anisyl alcohol (AA) rapidly quenched the 2Cl-1,4-DMB cation radical optical absorption bands, suggesting that the cation radical directly mediates the oxidation of AA. When LiP reactions are conducted in the presence of 50 microM 2Cl-1,4-DMB, the enzyme is inactivated; however, this inactivation can be prevented by the addition of AA. This also suggests that the 2Cl-1,4-DMB cation radical formed in the reaction, in turn, oxidizes AA.

Nitration of veratryl alcohol by lignin peroxidase and tetranitromethane

Lignin peroxidase (LiP), from Phanerochaete chrysosporium, in the presence of H2O2 and tetranitromethane (TNM), oxidizes veratryl (3,4-dimethoxybenzyl) alcohol (VA) (I) to veratraldehyde (IV), 4,5-dimethoxy-2-nitrobenzyl alcohol (V), and 3,4-dimethoxy-nitrobenzene (VI). The formation of these products is explained by a mechanism involving the one-electron oxidation of VA by LiP to produce the corresponding cation radical, which loses a proton to generate the benzylic radical. The latter reduces TNM to generate the trinitromethane anion (VIII) and the nitrogen dioxide radical (.NO2). .NO2 couples with the VA cation radical, and the subsequent loss of a proton leads to V. Alternatively, the attack of .NO2 at C-1 of the VA cation radical, followed by aromatization and loss of formaldehyde (VII), yields VI. Isotopic labeling experiments confirm that V is generated by the reaction of .NO2 with the VA cation radical, rather than with the benzylic radical. The nitration of two other LiP substrates, 1,4-dimethoxybenzene (II) and tyrosine (III), also was examined. Product analysis of reactions conducted in the presence of H2O2 with these substrates indicated less nitrated product was formed from 1,4-dimethoxybenzene and no nitrated product was formed from tyrosine. However, significant amounts of nitrated products were formed from 1,4-dimethoxybenzene and tyrosine when glucose and glucose oxidase were used as an H2O2 source. These results suggest that a reductant, either the veratryl alcohol benzylic radical or superoxide, is required in the reaction to reduce TNM to generate .NO2. These results provide further evidence for the formation of the VA cation radical and the first chemical evidence for the formation of the VA benzylic radical in LiP-catalyzed reactions.

Irreversible oxidation of ferricytochrome c by lignin peroxidase

Lignin peroxidase (LiP) from Phanerochaete chrysosporium catalyzes irreversible oxidative damage to ferricytochrome c (Cc3+) in the presence of H2O2 and 3,4-dimethoxybenzyl (veratryl) alcohol (VA). Atomic absorption analysis and UV/vis spectroscopy indicate that the oxidation of Cc3+ is accompanied by a loss of heme iron from the protein and probably oxidation of the porphyrin ring. At H2O2 concentrations of 7.5 microM or higher, this oxidation of Cc3+ by LiP is strictly dependent on the presence of VA. The latter is not oxidized to veratraldehyde at a significant rate in the presence of either ferrocytochrome c (Cc2+) or Cc3+, indicating it is not stimulating the reactions by specifically reducing LiP compound II. LiP is inactivated rapidly in 100 microM H2O2, and the presence of 500 microM VA protects LiP from this inactivation. Neither 20 microM Cc3+ nor 20 microM VA alone can protect LiP from inactivation; however, 20 microM each of VA and Cc3+ together protect LiP fully. This and other results strongly suggest that VA is acting as a protein-bound redox mediator in the oxidation of Cc3+. SDS-PAGE analysis of the Cc3+ oxidation products demonstrates the formation of some covalently linked dimer of Cc3+ in addition to the oxidized Cc3+ monomer. Amino acid analysis of the dimeric and monomeric products indicates the presence of oxidized Met and Tyr residues. This suggests that Tyr residues on the surface of the protein are oxidized to Tyr radicals during LiP oxidation and that some of these radicals subsequently undergo intermolecular radical coupling, resulting in dimerization of some of the Cc3+ molecules. However, most of the Cc3+ molecules appear to be irreversibly oxidized without dimerization. These results demonstrate that Cc3+ can serve as a useful polymeric model of the lignin substrate in studying the enzymatic mechanism of lignin oxidation and the role of VA in the reaction.

Haloperoxidase activity of manganese peroxidase from Phanerochaete chrysosporium

Manganese peroxidase (MnP) from Phanerochaete chrysosporium exhibits haloperoxidase activity at low pH. In the presence of hydrogen peroxide, MnP oxidizes bromide and iodide as measured by the formation of tribromide and triiodide complexes and the halogenation of various organic substrates. The optimum pHs for bromide and iodide oxidation are 2.5 and 3.0, respectively. Transient-state kinetic studies show that the reaction between MnP compound I and bromide or iodide occurs via a single two-electron step process, obeying second-order kinetics. The second-order rate constants for MnP compound I reduction by bromide and iodide are (4.1 +/- 0.2) x 10(3) and (1.1 +/- 0.1) x 10(5) m-1 s-1, respectively, at pH 3.0. MnP brominates a variety of aromatic substrates, including veratryl (3,4-di-methoxybenzyl) alcohol (I) to produce of 2-bromo-4,5-dimethoxybenzyl alcohol (II). MnP also hydrobrominates cinnamic acid (VI) to produce 2-bromo-3-hydroxyphenylpropionic acid (VII). With 3,4-dimethoxycinnamic acid (III) as the substrate, two bromination products are identified: trans-2-bromo-1-(3, 4-dimethoxyphenyl) ethylene (IV) and 2-bromo-3-(3, 4-dimethoxyphenyl)-3-hydroxypropionic acid (V). MnP also brominates 1,3-dicarbonyl compounds such as monochlorodimedone and malonic acid. Incubation of MnP with bromide and H2O2 in the absence of organic substrates results in enzyme inactivation. MnP binds halides to produce characteristic optical difference spectra. From these spectra, apparent dissociation constants at pH 3.0 are determined to be 0.13, 20, and 45 mm for fluoride, chloride, and bromide, respectively.

Purification and characterization of two manganese peroxidase isozymes from the white-rot basidiomycete Dichomitus squalens

Two manganese peroxidase isozymes, MnP1 and MnP2, were purified from the extracellular medium of ligninolytic cultures of Dichomitus squalens. The proteins were purified to homogeneity using DEAE-Sepharose chromatography and Mono Q fast protein liquid chromatography. MnP1 and MnP2 have molecular masses of 48000 and 48900 Da, respectively, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Both isozymes are glycoproteins and each contains one iron protoporphyrin IX as a prosthetic group. The pl values of MnP1 and MnP2 are 4.15 and 3.90, respectively. N-Terminal amino-acid analysis suggests that these proteins are encoded by distinct genes. The Soret bands of the native ferric enzymes (408 nm and 406 nm, respectively) are shifted to 434 nm in the reduced enzymes and to 422 nm in the reduced-CO complexes. EPR g-values of the native enzymes are essentially identical to those for other MnPs and lignin peroxidases, and they confirm the high-spin state of the iron. The addition of 1 equivalent of H2O2 to either of the native ferric isozymes yields spectra which are characteristic of compound 1. Successive additions of 1 equivalent of ferrocyanide and 1 equivalent of H2O2 to the native enzymes yield spectra which are characteristic of compound II. Both MnP isozymes oxidize Mn2+ to Mn3+ in the presence of organic acid chelators. The MnP isozymes are produced by D. squalens only when the cells are grown in the presence of Mn.