[Utility of measurement of tumor markers for preoperative staging of gastric cancer]

In 120 operated cases of gastric cancer, nine tumor makers (serum carcinoembryonic antigen (CEA), alpha-fetoprotein (AFP), carbohydrate antigen 19-9 (CA19-9), carbohydrate antigen 125 (CA125), tissue polypeptide antigen (TPA), serum beta 2-microglobulin (s-BMG), urine beta 2-microglobulin (mu-BMG), serum immunosuppressive acidic protein (IAP) and sialic acid (SA)) were determined before operation, to explore distribution patterns, positive rates, and relationships among these markers. And, we explored tumor markers which would be useful in preoperative assessment of the cancer stage and feasibility of radical treatment. The following results were obtained. 1. The distribution of all tumor markers was close to normal logarithmic distribution. 2. The positive rate was high in the order of IAP > TPA > CEA > CA19-9 >s-BMG > SA > u-BMG > CA125 > AFP. 3. Strong correlations were observed between IAP and SA, between CA125 and TPA. 4. The optimum combination of markers for diagnosis of the cancer stage was IAP + CA19-9 + CA125 and the optimum combination for assessment of the feasibility of radical treatment was IAP + CA125 + TPA.

[Cerebrovascular diseases due to extra- and intracranial atherosclerosis]

(1) In Japan, atherosclerosis in the extracranial arteries has now been more or less prevailing. (2) Many devices are widely used to extra- and intracranial vascular disease. However, such a simple sign as an auscultation of the carotid bruit or aortic-arch calcification in the X-ray picture may give valuable information of extra- and intracranial atherosclerosis. (3) Anti-heat-shock protein 64 antibody has recently been presented as an independent risk factor of carotid atherosclerosis. (4) Clinical features of carotid occlusion or stenosis are markedly variable. PET study has revealed that a water-shed ischemic zone may be in a state of "misery perfusion". (5) Regression may occur in the cervical as well as cerebral atherosclerosis.

Okadaic acid biologically mimics the role of calcium/phospholipid dependent kinase inhibitors in the process of HL-60 cell differentiation

Okadaic acid, a newly recognized protein phosphatase inhibitor and a non-TPA type tumor promoter, enhanced 1 alpha 25(OH)2D3(D3)-induced HL-60 cell differentiation into monocyte/macrophage lineage but did not affect dibutyryl cyclic AMP (dbcAMP)-induced differentiation into granulocytic lineage. Okadaic acid alone did not induce any differentiation. The process of D3-induced HL-60 cell differentiation on cultivation in magnesium deficient medium can be divided into two steps namely commitment and phenotypic expression as we have previously reported (J Cell Physiol 1987;131:50; Cell Growth Diff 1991;2:415), and the effect of okadaic acid on each step was studied. The results obtained indicated that okadaic acid inhibited commitment and enhanced phenotypic expression. We have previously shown that PKC has a dual action in the process of differentiation, i.e. as a positive regulatory signal in commitment and as a negative one in phenotypic expression. Thus, although okadaic acid has been reported to enhance the phosphorylation of various proteins that are also phosphorylated by PKC, we found that it mimics the role of PKC inhibitors such as H7 and staurosporine in D3-induced HL-60 cell differentiation.

[Clinical study of patients with deep-seated fungal infection associated with hematological diseases]

An assessment has been made regarding usefulness of measuring beta-D-glucan (beta-glucan) as fungal serodiagnosis in 50 cases of fungal infection with hematological diseases. Further, an assessment has been made regarding relation between hematological findings and therapeutic effect by administering miconazole, an antifungal agent (MCZ: Florid, clinically to the subjects. Positivity of beta-glucan (beta-glucan > or = 10 pg/ml) was observed in 54.5% (24/44), and the effective rate of MCZ in the positive cases was 75.0% (18/24). In the cases in whom fungus was detected, beta-glucan-positive rate was 50.0% (8/16), and MCZ-effective rate in beta-glucan-positive cases was 62.5% (5/8). The total effective rate of MCZ was 80% (40/50). Side effects were observed in 3 cases, but continual administration of MCZ was possible in all of the 3 cases. By the assessment regarding the relation between hematological findings and therapeutic effect of MCZ, it was found that the effective rates in the cases who underwent a transition with neutrophil and lymphocyte counts less than 500/microliters during the period of MCZ administration were 64.7% (11/17) and 50% (5/10), respectively, and large effects were observed in the cases who underwent a transition with the neutrophil and lymphocyte counts more than 500/microliters was 86.7% (19/22) and 91.7% (22/24), respectively. These results suggested that lymphocytes rather than neutrophils had an important role in the morbidity of fungal infection. It was noteworthy that MCZ was effective for the treatment of deep seated mycosis and significant effective rate was obtained in the group of patients who had neutrophils and lymphocytes less than 500/microliters.

High-molecular-weight protease complexes (proteasomes) of sperm of the ascidian, Halocynthia roretzi: isolation, characterization, and physiological roles in fertilization

It has been proposed that a chymotrypsin-like enzyme plays a key role in sperm penetration through the vitelline coat of eggs of the ascidian, Halocynthia roretzi. In this report, two kinds of chymotrypsin-like enzymes were isolated from spermatozoa of H. roretzi. Both enzymes were characterized as high-molecular-weight protease complexes that comprised several different subunits and that showed several different protease activities. Both showed immunoreactivity with anti-proteasome antibody. One showed properties characteristic of the 20 S proteasome and its molecular mass was 630 kDa, whereas the other protease complex of 930 kDa showed inhibitor susceptibility different from that of the 20 S proteasome. Upon the sperm reaction which is induced by treatment with high pH, the proteasomes were found to be released from sperm and they had the activity to digest the vitelline coats. These results suggest that the proteasomes are exposed extracellularly when sperm contact with the egg coat and may function as lysins in the fertilization process.

Cellular sensitivity to native type IV collagen in primary biliary cirrhosis

We examined 60 patients with various chronic liver diseases for cellular sensitivity to native human type I and IV collagens using an in vitro leucocyte migration inhibition test. Mononuclear cells from 7 (33%) of 21 patients with chronic active hepatitis, 14 (52%) of 27 patients with liver cirrhosis and 11 (92%) of 12 patients with primary biliary cirrhosis exhibited cellular sensitivity to type IV collagen, although cells from almost all patients responded to type I collagen. None except one for type I collagen of 25 normal controls showed positive response to both collagens. In chronic active hepatitis and liver cirrhosis, cellular sensitivity to type IV collagen was significantly lower than to type I collagen (p < 0.01). Patients with primary biliary cirrhosis showed significantly higher cellular sensitivity to type IV collagen when compared to patients with other chronic liver diseases (p < 0.01). Cellular sensitivity to type IV collagen was significantly correlated with serum levels of the 7S domain of type IV collagen in all 85 subjects (r = +0.462, p < 0.001). These findings suggest that cellular sensitivity to type IV collagen as well as to type I collagen exists in chronic liver disease, especially in primary biliary cirrhosis, and may reflect the accelerated metabolism of the perisinusoidal and peribiliary basement membranes.

Chemoprevention of oral carcinogenesis by DL-alpha-difluoromethylornithine, an ornithine decarboxylase inhibitor: dose-dependent reduction in 4-nitroquinoline 1-oxide-induced tongue neoplasms in rats

The modifying effect of three doses of DL-alpha-difluoromethylornithine (DFMO) given p.o. during the post-initiation phase of tongue carcinogenesis initiated by 4-nitroquinoline 1-oxide (4-NQO) was studied in male ACI/N rats. Animals were given 4-NQO at 20 ppm for 8 weeks in the drinking water to induce tongue neoplasms. One week after the stop of 4-NQO treatment, rats were transferred to the drinking water containing DFMO at concentrations of 100, 1000, and 2000 ppm for 25 weeks. The other groups consisted of rats given 2000 ppm DFMO alone or untreated rats. Thirty-four weeks after the start of the experiment, all animals were necropsied, and the incidences of neoplasms and preneoplastic lesions in the tongue, polyamine levels in the bloods and tongue tissues, and cell proliferation estimated by the number and area of silver-stained nucleolar organizer regions in the tongue epithelium were compared among the groups. Feeding of DFMO at all doses significantly inhibited the incidence of tongue neoplasms compared to the group given 4-NQO alone. DFMO at levels of 1000 and 2000 ppm significantly reduced the incidence of preneoplastic lesions of the tongue. Results analyzed by the linear regression method suggested a dose-dependent inhibition in the incidences of neoplastic and preneoplastic lesions of the tongue with increasing levels of DFMO. Increased levels in polyamines in the blood and tongue tissue were significantly suppressed by the treatment of DFMO. Also, silver-stained nucleolar organizer region indices were significantly reduced by the DFMO exposure. These results indicate that increasing levels of DFMO in the drinking water inhibited 4-NQO-induced tongue carcinogenesis in a dose-dependent manner and such inhibition was related to reduction in the polyamine levels of blood and tissue and decrease in the cell proliferation.

Surgical techniques and innovations in living related liver transplantation

The authors successfully performed a series of 33 living related liver transplantations (LRLT) on children (15 males and 18 females, ranging from 7 months to 15 years of age) from June 1990 to May 1992, with the informed consent of their parents and the approval of the Ethics Committee of Kyoto University. Before operation, six of the children required intensive care, another 14 were hospitalized, and 13 were homebound. Donors (12 paternal and 21 maternal) were selected solely from the parents of the recipients on the basis of ABO blood group and graft/recipient size matching determined by computed tomography scanning. Procurement of graft was performed using ultrasonic aspirator and bipolar electrocautery without blood vessel clamping and without graft manipulation. All donors subsequently had normal liver function and returned to normal life. The left lateral segment (16 cases), left lobe (16 cases), or right lobe (one case) were used as grafts. The partial liver graft was transplanted into the recipient who underwent total hepatectomy with preservation of the inferior vena cava using a vascular side clamp. Twenty-seven of 33 recipients are alive and well with the original graft and have normal liver function. The patient survival rate was 89% (24/27) in elective cases and 50% (3/6) in emergent cases. The other six recipients had functioning grafts but died of extrahepatic complications. Complications of the graft were minimal in all cases. Hepatic vein stenosis, which occurred three times in two cases, was successfully treated by balloon dilatation. In cases with sclerotic portal vein, the authors anastomosed the portal vein of the graft to the confluence of the splenic vein and the superior mesenteric vein without a vascular graft, after experiencing a case of vascular graft thrombosis. After hepatic artery thrombosis occurred in one of the initial seven recipients whose arterial anastomosis was done with surgical loupe, microsurgery was introduced for hepatic artery reconstruction. There has been no occurrence of thrombosis since then. The current results with LRLT suggested that the meticulous management of surgical factors at each stage of the LRLT procedure is crucial for successful outcome. Living related liver transplantation is a promising option for resolving the graft shortage in pediatric liver transplantation and may be regarded as an independent modality to supplement cadaver donation.

Adult neuroblastoma in pregnancy: report of a case

We report herein an extremely rare case of retroperitoneal neuroblastoma occurring in a mother during her third trimester of pregnancy. A live male infant was delivered by cesarean section at 36 weeks gestation and 23 days later, the mother's tumor was curatively resected. Six months have elapsed since her operation and there has been no evidence of tumor recurrence. Adult neuroblastoma is an uncommon malignancy and, to our knowledge, there has been no case of this tumor occurring in pregnancy ever described in the English literature. The diagnosis, treatment, and follow-up of this neoplasm and its association with pregnancy are discussed in this report.

The properties of monoclonal antibody against sepiapterin reductase from fat body of the silkworm, Bombyx mori

A specific monoclonal antibody prepared for the 29-kDa a subunit of silkworm fat body sepiapterin reductase (SPR) was able to recognize the subunit in crude extract of fat body after SDS treatment. Although SPR from the silkworm fat body has biochemical properties similar to those reported for SPR from mammalian sources, especially rat erythrocytes, the antibody failed to recognize the 28-kDa subunit of rat erythrocyte SPR. This result indicates that SPR from silkworm fat body has a different amino-acid sequence from that of the rat erythrocyte enzyme. Sepiapterin reductase activity has not been found in crude extract of fat body from the silkworm mutant lemon. Although the antibody recognized only 29-kDa protein in the crude extract of silkworm fat body from normal strain after SDS-treatment, the antibody recognized only an approximately 80-kDa protein in the crude extract of the lemon mutant after SDS-treatment.

Modification of pig liver dimeric dihydrodiol dehydrogenase with diethylpyrocarbonate and by rose bengal-sensitized photooxidation: evidence for an active-site histidine residue

Dihydrodiol dehydrogenase from pig liver was inactivated by diethylpyrocarbonate (DEP) and by rose bengal-sensitized photooxidation. The DEP inactivation was reversed by hydroxylamine and the absorption spectrum of the inactivated enzyme indicated that both histidine and tyrosine residues were carbethoxylated. The rates of inactivation by DEP and by photooxidation were dependent on pH, showing the involvement of a group with a pKa of 6.4. The kinetics of inactivation and spectrophotometric quantification of the modified residues suggested that complete inactivation was caused by modification of one histidine residue per active site. The inactivation by the two modifications was partially prevented by either NADP(H) or the combination of NADP+ and substrate, and completely prevented in the presence of both NADP+ and a competitive inhibitor which binds to the enzyme-NADP+ binary complex. The DEP-modified enzyme caused the same blue shift and enhancement of NADPH fluorescence as did the native enzyme, suggesting that the modified histidine is not in the coenzyme-binding site of the enzyme. The results suggest the presence of essential histidine residues in the catalytic region of the active site of pig liver dihydrodiol dehydrogenase.

SPECT findings in Parkinson's disease associated with dementia

Dementia in Parkinson's disease is thought to be attributable not only to subcortical lesions but also to cortical alterations, especially frontal lobe dysfunction. To evaluate cortical function, the regional cerebral blood flow (rCBF) was estimated of 13 demented and 13 non-demented age matched patients with Parkinson's disease compared with that of 10 age matched controls using I-123 iodoamphetamine single photon emission tomography (IMP-SPECT). The rCBF of the nondemented Parkinson's patients showed no significant differences from that of the control subjects. In the demented patients, the bilateral frontal and parietal and left temporal regional blood flow was significantly less than in the controls. Four demented patients showed isolated frontal hypoperfusion, 8 showed fronto-parietal hypoperfusion, and 1 showed isolated parietal hypoperfusion. Frontal hypoperfusion was therefore present in 12 of the 13 demented patients, and this finding agrees with the frontal lobe dysfunction hypothesis. Parietal rCBF had a significant positive correlation with cortical functions such as calculation and language ability in the MMSE scores. The parietal and temporal reduction in rCBF probably reflects the presence of Alzheimer pathology, cortical Lewy body disease, or both.

The potential for the development of liver metastasis from alpha-fetoprotein-producing human gastric carcinomas in nude mice

The potential for liver metastasis in addition to the transplantability and doubling time of alpha-fetoprotein(AFP)-producing and non-AFP-producing human gastric carcinomas were studied in nude mice. The potential for liver metastasis was analyzed histopathologically from intrasplenic injections of tumor cell suspensions prepared from subcutaneous tumors. Tumor fragments prepared aseptically from 15 AFP-producing and 140 non-AFP-producing gastric cancers were subcutaneously transplanted into nude mice with transplantability rates of 80% (12/15 cases) and 50% (70/140 cases), respectively. The mean tumor doubling times in the first generation were 10.6 days for AFP-producing and 13.2 days for non-AFP-producing gastric carcinomas. Serially transplantable tumor lines in nude mice were established from six AFP-producing and 10 non-AFP-producing carcinomas. When tumor cell suspensions prepared from the subcutaneous tumors were injected into spleens, all six AFP-producing carcinomas (two poorly differentiated and four tubular adenocarcinomas) but only four out of the 10 non-AFP-producing carcinomas (two poorly differentiated adenocarcinomas, one mucinous carcinoma and one papillary adenocarcinoma) demonstrated a potential for liver metastasis. The results indicate AFP-producing gastric carcinomas to possess a higher potential for liver metastasis than do non-AFP-producing carcinomas, a distinguishing feature which thus reflects a poor prognosis.

The 26 S proteasome is activated at two points in the ascidian cell cycle

The proteasome undergoes cell cycle-dependent changes in its subcellular distribution during ascidian embryonic development [(1992) Dev. Biol. 151, 27-33]. In this study, we demonstrate that the 26 S proteasome is markedly activated in both prophase and metaphase of the mitotic cell cycle in the ascidian embryos in comparison with the case of the 20 S proteasome. These results suggest that the 26 S proteasome is activated and participates in proteolysis at the restricted stages of the cell cycle.

Phorbol ester alters carbachol-stimulated diacylglycerol formation in parotid acinar cells through the hydrolysis of phosphoinositides and phosphatidylcholine

Incubation of rat parotid acinar cells with phorbol 12,13-dibutyrate (PDBu) resulted in inhibition of carbachol-stimulated formation of sn-1,2-diacylglycerol (DAG). PDBu pretreatment inhibited carbachol-induced turnover of phosphoinositides; this inhibition was indicated by phosphatidylinositol 4,5-bisphosphate breakdown. This pretreatment also attenuated the effect of carbachol on inositol phosphate generation and phosphatidylcholine hydrolysis. These results show that PDBu alters carbachol-stimulated DAG formation through the hydrolysis of phosphoinositides and phosphatidylcholine.

Chemical modification of cysteinyl, lysyl and histidyl residues of mouse liver 17 beta-hydroxysteroid dehydrogenase

Monomeric 17 beta-hydroxysteroid dehydrogenase from mouse liver was rapidly inactivated by 5,5'-dithiobis(2-nitrobenzoic acid) and 2,4,6-trinitrobenzene-1-sulfonate, and the absorption spectra of the inactivated enzymes indicated that cysteine and lysine residues were modified. The kinetics of inactivation and spectrophotometric quantification of the modified residues suggested that complete inactivation was caused by modification of two cysteine residues or one lysine residue per active site. The inactivation by the two reagents was protected by NADP+ and some coenzyme analogs, but not by a steroid substrate, testosterone. Moreover, chemical modification by diethyl pyrocarbonate also produced inactivation of the enzyme, and showed a difference spectrum with a peak at 242 nm characteristic of N-carbethoxyhistidine residues, which decreased with the addition of hydroxylamine. The inactivation by this reagent, following pseudo-first-order kinetics, was protected partially by either NADP+ or testosterone and completely in the presence of both the coenzyme and substrate. The results suggest the presence of essential cysteine and lysine residues at or near the coenzyme-binding site and that of essential histidine residue(s) in the catalytic region of the active site of mouse liver 17 beta-hydroxysteroid dehydrogenase.

Participation of 650-kDa protease (20 S proteasome) in starfish oocyte maturation

A protease involved in oocyte maturation of a starfish, Asterina pectinifera, was explored. Trypsin-like and chymotrypsin-like activities of the 650-kDa protease in oocyte extract were revealed to increase more than twice under the influence of 1-methyladenine before germinal vesicle breakdown (GVBD) during maturation. The inhibitory potencies of leupeptin and its five analogs against the chymotrypsin-like activity, but not the trypsin-like activity, of this protease was well in accord with those against GVBD (Takagi Sawada et al. (1989). Dev. Biol. 133, 609-612). These results indicate that the chymotrypsin-like activity of the 650-kDa protease (most probably 20 S proteasome) plays a key role in starfish oocyte maturation.

[Autonomic dysfunction of central nervous system disorders]

Central nervous system disorders, such as cerebrovascular or spinal cord lesions often cause dysfunctions of the autonomic nervous system. In most cases of acute cerebrovascular accidents, blood pressure is transiently elevated. Some patients, especially with pontine or thalamic hemorrhage, suffer from extremely high fever. In patients with large lesions in the cerebral hemisphere or lesions in the brainstem, cardiopulmonary state may be affected. In spite of absence of acute myocardial infarction, electrocardiogram may show ST-T changes resembling acute myocardial infarction. Cheyne-Stokes respiration or sleep apnea can occur. Lesions in the medulla oblongata cause dysfunctions of automatic respiration. Patients with large cerebrovascular lesions in the unilateral hemisphere often show transient hyperhidrosis on the contralateral side. Prognosis of patients with these autonomic failures is poor. In patients with spinal shock, blood pressure and heart rate are reduced. In chronic stage, autonomic hyperreflexia, such as attacks of episodic hypertension can occur. Lesions in the high cervical cord often bring nonsymptomatic perforating gastric ulcer.

Structural and functional comparison of two human liver dihydrodiol dehydrogenases associated with 3 alpha-hydroxysteroid dehydrogenase activity

Two monomeric dihydrodiol dehydrogenases with pI values of 5.4 and 7.6 were co-purified with androsterone dehydrogenase activity to homogeneity from human liver. The two enzymes differed from each other on peptide mapping and in their heat-stabilities; with respect to the latter the dihydrodiol dehydrogenase and 3 alpha-hydroxysteroid dehydrogenase activities of the respective enzymes were similarly inactivated. The pI 5.4 enzyme was equally active towards trans- and cis-benzene dihydrodiols, and towards (S)- and (R)-forms of indan-1-ol and 1,2,3,4-tetrahydronaphth-1-ol and oxidized the 3 alpha-hydroxy group of C19-, C21- and C24-steroids, whereas the pI 7.6 enzyme showed high specificity for trans-benzene dihydrodiol, (S)-forms of the alicyclic alcohols and C19- and C21-steroids. Although the two enzymes reduced various xenobiotic carbonyl compounds and the 3-oxo group of C19- and C21-steroids, and were A-specific in the hydrogen transfer from NADPH, only the pI 5.4 enzyme showed reductase activity towards 7 alpha-hydroxy-5 beta-cholestan-3-one and dehydrolithocholic acid. The affinity of the two enzymes for the steroidal substrates was higher than that for the xenobiotic substrates. The two enzymes also showed different susceptibilities to the inhibition by anti-inflammatory drugs and bile acids. Whereas the pI-5.4 enzyme was highly sensitive to anti-inflammatory steroids, showing mixed-type inhibitions with respect to indan-1-ol and androsterone, the pI 7.6 enzyme was inhibited more potently by non-steroidal anti-inflammatory drugs and bile acids than by the steroidal drugs, and the inhibitions were all competitive. These structural and functional differences suggest that the two enzymes are 3 alpha-hydroxysteroid dehydrogenase isoenzymes.

Purification and characterization of pig lung carbonyl reductase

A pyrazole-sensitive carbonyl reductase from pig lung was purified to homogeneity by electrophoretic criteria. Chemical cross-linking study suggested that the native enzyme is a tetramer with a Mr of 103,000, consisting of apparent identical subunits of Mr 24,000. The enzyme reduced aliphatic and aromatic carbonyl compounds with NADPH as a preferable cofactor to NADH and catalyzed the oxidation of secondary alcohols and the aldehyde dismutation in the presence of NAD(P)+. Immunohistochemical study with the antibodies against the enzyme revealed that the enzyme was localized in the ciliated cells, nonciliated bronchiolar cells, Type II alveolar pneumocytes, and the epithelial cells of the ducts of the bronchial glands in the pig lung. In addition to the properties and distribution, the pig lung enzyme was immunochemically similar to the pulmonary enzymes in the guinea pig and mouse. However, the pig enzyme showed the following unusual features. (1) The enzyme exhibited an equatorial specificity in the reduction of 3-ketosteroids; the 4-pro-S hydrogen of NADPH was transferred to the carbonyl carbon atom of 5 alpha- and 5 beta-androstanes, and the respective reduced products were identified as 3 beta- and 3 alpha-hydroxysteroids. (2) Although the NADPH-linked reduction of carbonyl compounds apparently obeyed the Michaelis-Menten kinetics at pH 6.0, the double-reciprocal plots of the velocity vs concentrations of the carbonyl substrates were convex at pH higher than 6.5. The Hill coefficients and [S]0.5 values for the substrates decreased as the pH for reaction increased. The results suggest that the pig enzyme exhibits negative cooperativity with respect to the carbonyl substrates and that the hydrogen ion acts as an allosteric effector abolishing the negative interaction.

Activation of carbonyl reductase from pig lung by fatty acids

The NADPH-linked reductase activity of pig lung carbonyl reductase was activated two- to fivefold by fatty acids with a carbon chain length greater than nine at pH 7.0. cis-Unsaturated fatty acids of C:18 and C:20 were potent activators, showing Ka values of 2-14 microM which were lower than the values of 21-125 microM for saturated fatty acids (C:9 to C:16). Of the fatty acids arachidonic acid (C20:4) gave the highest activation. No significant stimulatory effect was observed with acyl CoAs, fatty alcohols, phospholipids, and nonionic detergents. Anionic detergents (sodium dodecyl sulfate and sarkosyl) stimulated the enzyme activity more than ninefold, but the Ka values for them were much higher than those for the cis-unsaturated fatty acids. Although no change in molecular weight or in subunit composition was observed in the enzyme activated by C20:4, the activation led to a decrease in thermal stability of the enzyme. The binding of C20:4 to the enzyme was instantaneous and reversible, shifted the pH optimum of the activity from 5.8 to 6.5, and changed the inhibitor sensitivity. In addition, C20:4 acted as an allosteric effector abolishing the negative interaction of the enzyme with carbonyl substrates which was seen without the fatty acid, but the activation increased both Vmax and [S]0.5 values for the substrates. Kinetic analysis with respect to NADPH concentration, in which no cooperativity was detected with or without C20:4, indicated that C20:4 was a nonessential activator of mixed type showing a binding constant of 10 microM. These results suggest that cis-unsaturated fatty acids may be potential modulators of pulmonary carbonyl reductase.