Differential effects of methylmethane thiosulfonate on rat liver GPAT and DHAPAT
Subcellular fractions (mitochondrial (M), light-mitochondrial (L), and microsomal) from rat liver were treated with 5 mM methylmethane thiosulfonate (MMTS) or 50 ..mu..M N-ethylmaleimide (NEM). Both of these reagents are known to specifically modify cysteine residues in proteins. After treatment, samples of each fraction were assayed for glycerophosphate acyltransferase and dihydroxyacetone phosphate acyltransferase activities. As reported by others, NEM was found to inhibit GPAT in the microsomal fraction but had no effect on this enzyme in the M or L fractions. MMTS, on the other hand, inhibited GPAT in all fractions to the extent of 80-100% compared to activity in untreated samples. DHAPAT activity in each fraction showed little or no inhibition by either reagent. Only the microsomal DHAPAT activity showed any sensitivity at all, being inhibited by 10-12% by both NEM and MMTS. This is the first demonstration of inhibition of mitochondrial GPAT by a thiol-specific reagent and is an indication that, like the microsomal analog, this enzyme may have a cysteine residue at or near the active site. In addition, these results are further evidence for the premise that DHAPAT and GPAT are separate and distinct proteins.
- Research Organization:
- Univ. of Michigan, Ann Arbor
- OSTI ID:
- 6065545
- Report Number(s):
- CONF-870644-
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 46:6; Conference: 78. annual meeting of the American Society of Biological Chemists conference, Philadelphia, PA, USA, 7 Jun 1987
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
METHYL METHANESULFONATE
METABOLISM
NEM
TRANSFERASES
ENZYME ACTIVITY
CYSTEINE
INHIBITION
LIVER
MICROSOMES
MITOCHONDRIA
RATS
REAGENTS
AMINO ACIDS
ANIMALS
ANTIMITOTIC DRUGS
BODY
CARBOXYLIC ACIDS
CELL CONSTITUENTS
DIGESTIVE SYSTEM
DRUGS
ENZYMES
ESTERS
GLANDS
IMIDES
MAMMALS
MUTAGENS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
ORGANOIDS
ORGANS
RADIOSENSITIZERS
RODENTS
SULFONIC ACID ESTERS
THIOLS
VERTEBRATES
560300* - Chemicals Metabolism & Toxicology