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Triose phosphates as precursors of glyceride biosynthesis by rat liver microsomes
Author(s) -
Puleo L. E.,
Ananda Rao G.,
Reiser R.
Publication year - 1970
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02531391
Subject(s) - dihydroxyacetone phosphate , dhap , triosephosphate isomerase , glycerol kinase , microsome , glycerol 3 phosphate dehydrogenase , glycerol , glyceride , glyceraldehyde , nad+ kinase , biochemistry , phosphatidate , chemistry , dehydrogenase , phosphate , diacylglycerol kinase , enzyme , fatty acid , protein kinase c
Washed rat liver microsomes synthesize phosphatidate and di‐ and triglycerides from dihydroxyacetone phosphate (DHAP) or DL‐glyceraldehyde 3‐phosphate (DL‐GAP) and fatty acids. The cofactors required in either case are ATP, CoASH, Mg ++ , and either NADH or NADPH. NADH is twice as active as NADPH. In the presence of γ‐ 32 P‐ATP, 1‐ 14 C‐palmitate, CoASH and NADH, the combined actions of glycerol kinase (ATP‐glycerol phosphotransferase EC 2.7.1.30), and microsomes convert dihydroxyacetone to phosphatidate with the molar ratio of 14 C∶ 32 P approximately 2∶1. Since glycerol 3‐phosphate dehydrogenase (L‐glycerol 3‐phosphate: NAD oxidoreductase EC 1.1.1.8) is not present in microsomes, the synthesis of glycerides from either DHAP or GAP need not occur via their conversion to glycerol 3‐phosphate (GP). However, the presence of triose phosphate isomerase (D‐glyceraldehyde 3‐phosphate:ketol‐isomerase EC 5.3.1.1) in microsomes, suggests the conversion of GAP to DHAP during glyceride synthesis. The requirement for this conversion was confirmed by the use of 1‐hydroxy‐3‐chloro‐2‐propanone phosphate (HCPP), an irreversible inhibitor of triose phosphate isomerase. The synthesis of glycerides from DL‐GAP was completely inhibited by HCPP, whereas that from DHAP was not.