Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phosphatidylserine decarboxylase, Escheichia coli, was purified to near-homogeneity by the procedure of Dowhan, W., Wickner, W. T., and Kennedy, E. P. ((1974) J. Biol. Chem. 249, 3079-3084) and assayed by following the production of CO2 using gas chromatography. The purified enzyme has an absolute requirement for the surfactant Triton X-100. The function of Triton in the assay is evaluated and a kinetic scheme describing the action of this membrane-bound enzyme in the micellar system provided by the surfactant is presented. According to this scheme, the enzyme first binds to a mixed micelle, composed of phosphatidylserine and Triton, where the dissociation constant is KSA. The enzyme, now part of the mixed micelle, then binds the substrate phosphatidylserine in its active site and this binding is related to the Michaelis constant, KMB. KSA, expressed as the sum of the molar concentrations of Triton and phosphatidylserine, is about 0.04 M. KMB, expressed as the mole fraction of phosphatidylserine in the mixed micelles, is about 0.03. Phosphatidylserine decarboxylase activity toward phosphatidylserine in human erythrocyte ghosts was also determined. The amount of phsophatidylserine converted to phosphatidylethanolamine and CO2 was found to be related to the amount of phosphatidylserine solubilized from the membrane by Triton X-100. In the absence of Triton, no significant activity of the enzyme toward the ghosts was detected even after subjecting the ghosts to lyophilization, homogenization, or sonication.
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PMID:Action of the highly purified, membrane-bound enzyme phosphatidylserine decarboxylase Escherichia coli toward phosphatidylserine in mixed micelles and erythrocyte ghosts in the presence of surfactant. 110 Jun 27

Phosphatidylserine decarboxylase from Escherichia coli, an intrinsic membrane protein, catalyzes the conversion of phosphatidylserine to phosphatidylethanolamine. The physical and kinetic properties of the purified enzyme were studied in several detergents under assay conditions. The active form of the enzyme is an oligomer, probably a trimer, and the enzyme activity was unaffected by the concentration of the nonionic poly(oxyethylene) ether detergent present in the assay medium, so long as the detergent micelle/substrate mole ratio was less than one. When this ratio was greater than one, the detergent acted as an inhibitor by competing with enzyme-containing micelles for substrate. The zwitterionic and bile salt detergents that were tested inactivated the enzyme by dissociating the oligomer. The native, Triton X-100 solubilized, enzyme was modified with a cross-linking reagent. Activity of the cross-linked enzyme was retained after the Triton X-100 was replaced by a zwitterionic sulfobetaine detergent and conformed to the same kinetic model as with the poly(oxyethylene) ether detergents. The cross-linked enzyme was also active when solubilized by the bile salt detergents although the activity did not conform to any simple kinetic model. These data indicate that the oligomer is the active form of the enzyme under assay conditions and that certain nondenaturing detergents can inactivate this enzyme by dissociating the enzyme complex.
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PMID:Kinetics and protein subunit interactions of Escherichia coli phosphatidylserine decarboxylase in detergent solution. 701 77

A significant portion of brain phosphatidylethanolamine (PE) is synthesized by a pathway involving the mitochondrial enzyme phosphatidylserine decarboxylase (PSDC), in a process by which phosphatidylserine (PS) is transferred from the endoplasmic reticulum to mitochondria. Aging changes the fatty acid composition of brain phospholipids, PS and PE being the most affected. The present study was carried out to determine PSDC activity in cerebral cortex (CC) and cerebellum (CRBL) mitochondrial fraction from adult (4-month-old) and aged (30-month-old) rats and to compare these activities with that found in liver. To study the effect of 22:6n-3 content on the PSDC activity, PSs from different sources were prepared: rPS (from bovine retina, containing 36 mol % of 22:6n-3); adPS (from adult rat CC microsomal membranes, with 25 mole % 22:6n-3 content) and agPS (from aged rat CC microsomal membranes, with 21 mole % 22:6n-3 content). For aged CC PSDC, the preferred substrate was agPS (the physiological substrate for aged animals), whereas in adult CC PSDC the substrate preference was inverse (rPS > adPS > agPS). Furthermore, CRBL PSDC does not show any substrate preference based on 22:6n-3 content. CRBL PSDC activity in aged membranes using agPS as substrate is lower than PSDC activity in adult membranes in the presence of adPS. These results indicate that under physiological conditions, cerebellar PSDC is inhibited during aging. Liver PSDC activity showed the same substrate preference in adult and aged rats as adult CC PSDC. These findings lead us to conclude that PSDC activity has a differential tissue-dependent substrate preference characteristic of the aging process.
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PMID:Age-related changes in central nervous system phosphatidylserine decarboxylase activity. 1239 87