Abstract
CoA-dependent transacylation activity in microsomes catalyzes the transfer of fatty acid between phospholipids and lysophospholipids in the presence of CoA without the generation of free fatty acid. We examined the mechanism of the transacylation system using partially purified acyl-CoA:lysophosphatidylinositol (LPI) acyltransferase (LPIAT) from rat liver microsomes to test our hypothesis that both the reverse and forward reactions of acyl-CoA:lysophospholipid acyltransferases are involved in the CoA-dependent transacylation process. The purified LPIAT fraction exhibited ATP-independent acyl-CoA synthetic activity and CoA-dependent LPI generation from PI, suggesting that LPIAT could operate in reverse to form acyl-CoA and LPI. CoA-dependent acylation of LPI by the purified LPIAT fraction required PI as the acyl donor. In addition, the combination of purified LPIAT and recombinant lysophosphatidic acid acyltransferase could reconstitute CoA-dependent transacylation between PI and phosphatidic acid. These results suggest that the CoA-dependent transacylation system consists of the following: 1) acyl-CoA synthesis from phospholipid through the reverse action of acyl-CoA:lysophospholipid acyltransferases; and 2) transfer of fatty acyl moiety from the newly formed acyl-CoA to lysophospholipid through the forward action of acyl-CoA:lysophospholipid acyltransferases.
Highlights
CoA-dependent transacylation activity in microsomes catalyzes the transfer of fatty acid between phospholipids and lysophospholipids in the presence of CoA without the generation of free fatty acid
The combination of purified LPI acyltransferase (LPIAT) and recombinant lysophosphatidic acid acyltransferase could reconstitute CoA-dependent transacylation between PI and phosphatidic acid. These results suggest that the CoA-dependent transacylation system consists of the following: 1) acyl-CoA synthesis from phospholipid through the reverse action of acylCoA:lysophospholipid acyltransferases; and 2) transfer of fatty acyl moiety from the newly formed acyl-CoA to lysophospholipid through the forward action of acylCoA:lysophospholipid acyltransferases
We hypothesized that the CoA-dependent transacylation system consists of the following: 1) acyl-CoA synthesis through the reverse action of acyl-CoA: lysophospholipid acyltransferases; and 2) the transfer of a fatty acyl moiety from the newly formed acyl-CoA to lysophospholipid through the forward action of the acyltransferases (Scheme 1)
Summary
The combination of purified LPIAT and recombinant lysophosphatidic acid acyltransferase could reconstitute CoA-dependent transacylation between PI and phosphatidic acid These results suggest that the CoA-dependent transacylation system consists of the following: 1) acyl-CoA synthesis from phospholipid through the reverse action of acylCoA:lysophospholipid acyltransferases; and 2) transfer of fatty acyl moiety from the newly formed acyl-CoA to lysophospholipid through the forward action of acylCoA:lysophospholipid acyltransferases. We concluded that CoA-dependent transacylation activity toward LPA is catalyzed by a combination of the reverse and forward reactions of LPAAT (Scheme 1) These results suggested that the hypothesis is correct for LPAAT. Purified LPIAT catalyzed ATP-independent acyl-CoA synthetic activity with PI These results are consistent with the CoA-dependent transacylation activity toward LPI being because of a combination of the reverse and forward reactions of LPIAT. We conclude that the CoA-dependent transacylation activity is because of the combination of the reverse and forward reactions of acyl-CoA acyltransferases
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