Biomaterial Database

Inactivation of microsomal 17 beta-hydroxysteroid dehydrogenase by phospholipase C: rates of phospholipid hydrolysis and enzyme inactivation, and effects of phospholipids. 1982

C H Blomquist, and C E Kotts, and E Y Hakanson

When guinea-pig liver microsomes were exposed to phospholipase C the rate of phospholipid hydrolysis exceeded the rate of decrease in 17 beta-hydroxysteriod dehydrogenase (17 beta-HSD) activity. The time-course of the decrease in 17 beta-HSD activity was biphasic. An initial more rapid decrease (30-50% of total) was associated with the major extent (85%) of phospholipid hydrolysis. Subsequently, a second, slower phase of 17 beta-HSD inactivation was observed. The addition of purified phospholipids did not reactivate 17 beta-HSD but did protect against the inactivation seen in the second phase. The diacyglycerides produced by phospholipase C action remained associated with the microsomes. It is proposed that the differences in the rates of 17 beta-HSD inactivation reflect variations in the distribution of a single form of 17 beta-HSD among differing membrane fractions rather than the existence of multiple enzyme forms. The stabilizing effects of phospholipids may be due to their ability to prevent changes in lipid-lipid, lipid-protein and protein-protein interactions resulting from diacylglyceride formation. Resuspended microsomal lipids (chloroform-methanol extracts) inactivated 17 beta-HSD suggestive of the presence of endogenous lipid modulators of enzymatic activity.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008862	Microsomes, Liver	Closed vesicles of fragmented endoplasmic reticulum created when liver cells or tissue are disrupted by homogenization. They may be smooth or rough.	Liver Microsomes,Liver Microsome,Microsome, Liver
D010712	Phosphatidic Acids	Fatty acid derivatives of glycerophosphates. They are composed of glycerol bound in ester linkage with 1 mole of phosphoric acid at the terminal 3-hydroxyl group and with 2 moles of fatty acids at the other two hydroxyl groups.	Ammonium Phosphatidate,Diacylglycerophosphates,Phosphatidic Acid,Acid, Phosphatidic,Acids, Phosphatidic,Phosphatidate, Ammonium
D010713	Phosphatidylcholines	Derivatives of PHOSPHATIDIC ACIDS in which the phosphoric acid is bound in ester linkage to a CHOLINE moiety.	Choline Phosphoglycerides,Choline Glycerophospholipids,Phosphatidyl Choline,Phosphatidyl Cholines,Phosphatidylcholine,Choline, Phosphatidyl,Cholines, Phosphatidyl,Glycerophospholipids, Choline,Phosphoglycerides, Choline
D010738	Type C Phospholipases	A subclass of phospholipases that hydrolyze the phosphoester bond found in the third position of GLYCEROPHOSPHOLIPIDS. Although the singular term phospholipase C specifically refers to an enzyme that catalyzes the hydrolysis of PHOSPHATIDYLCHOLINE (EC 3.1.4.3), it is commonly used in the literature to refer to broad variety of enzymes that specifically catalyze the hydrolysis of PHOSPHATIDYLINOSITOLS.	Lecithinase C,Phospholipase C,Phospholipases, Type C,Phospholipases C
D010740	Phospholipases	A class of enzymes that catalyze the hydrolysis of phosphoglycerides or glycerophosphatidates. EC 3.1.-.	Lecithinases,Lecithinase,Phospholipase
D010743	Phospholipids	Lipids containing one or more phosphate groups, particularly those derived from either glycerol (phosphoglycerides see GLYCEROPHOSPHOLIPIDS) or sphingosine (SPHINGOLIPIDS). They are polar lipids that are of great importance for the structure and function of cell membranes and are the most abundant of membrane lipids, although not stored in large amounts in the system.	Phosphatides,Phospholipid
D002499	Centrifugation, Density Gradient	Separation of particles according to density by employing a gradient of varying densities. At equilibrium each particle settles in the gradient at a point equal to its density. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Centrifugations, Density Gradient,Density Gradient Centrifugation,Density Gradient Centrifugations,Gradient Centrifugation, Density,Gradient Centrifugations, Density
D006168	Guinea Pigs	A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research.	Cavia,Cavia porcellus,Guinea Pig,Pig, Guinea,Pigs, Guinea
D006868	Hydrolysis	The process of cleaving a chemical compound by the addition of a molecule of water.