PAF biosynthesis: Characterization of alkylacetyl-GP phosphohydrolase in rat spleens

Conference · Fri May 01 04:00:00 EDT 1987 · Federation Proceedings, Federation of American Societies for Experimental Biology; (USA)

OSTI ID:5075098

Malone, B; Lee, T C; Snyder, F ^[1]

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1. Oak Ridge Associated Univ., TN (USA)

The authors have characterized an alkylacetyl-GP phosphohydrolase in rat spleen microsomes that catalyzes the conversion of alkylacetyl-GP to alkylacetyl-G, a precursor of PAF. This enzyme has an optimal pH of 7.0, an apparent K{sub m} of 31.8 {mu}M, and is widely distributed in various tissues. Studies on substrate specificities, cation requirements, and the subcellular distribution of the alkylacetyl-GP phosphohydrolase suggest that this enzyme can be distinguished from a nonspecific phosphomonoesterase or phosphatidate phosphohydrolase. Like alkyllyso-GP:acetyl-CoA acetyltransferase, the alkylacetyl-GP phosphohydrolase shows no notable substrate selectivities with regard to variations in alkyl chain length at the sn-1 position or short-chain acyl groups (with the exception of C{sub 3:0}) at the sn-2 position of the glycerol molecule. The enzymatic activity of alkylacetyl-GP phosphohydrolase is 30- to 90-fold higher than alkyllyso-GP:acetyl-CoA acetyltransferase in most tissues. Also, alkylacetyl-GP phosphohydrolase can degrade alkyllyso-GP. Thus, our findings imply that specificities of the molecular species of PAF synthesized de novo are determined by the DTT-insensitive alkylacetyl-G:CDP-choline cholinephosphotransferase, the final step of the pathway. Furthermore, alkyllyso-GP:acetyl-CoA acetyltransferase appears to be the rate-limiting step in the de novo synthesis of alkylacetyl-G.

• OSTI ID: 5075098
• Report Number(s): CONF-870644--
• Conference Information: Journal Name: Federation Proceedings, Federation of American Societies for Experimental Biology; (USA) Journal Volume: 46:6
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
ANIMALS
BIOCHEMICAL REACTION KINETICS
BIOSYNTHESIS
BODY
CELL CONSTITUENTS
DRUGS
ENZYME ACTIVITY
ENZYMES
HEMATOLOGIC AGENTS
KINETICS
MAMMALS
MICROSOMES
MIXED-FUNCTION OXIDASES
ORGANOIDS
ORGANS
OXIDOREDUCTASES
OXYGENASES
PH VALUE
PRECURSOR
RATS
REACTION KINETICS
RIBOSOMES
RODENTS
SPLEEN
SUBSTRATES
SYNTHESIS
VERTEBRATES