A model for studying LCAT reaction: In vitro cholesterol esterification in pig ovarian follicular fluid

J. K. Yao, S. C S Chang, R. J. Ryan, Peter J Dyck

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Phosphatidylcholine acyltransferase (lecithin:cholesterol acyltransferase or LCAT; EC 2.3.1.43) activity was found to be present in pig ovarian follicular fluid (POFF), in addition to pig serum (PS). The cholesterol esterification rate in both POFF and PS is linear with incubation time up to 2 hr. The mean absolute rate of POFF-cholesterol esterification was 8.1 ± 0.4 nmoles per ml per hr approximately one-fourth of that in PS. However, the fractional rate (percent of labeled cholesterol esterified per hr) of POFF-cholesterol esterification was similar to that observed in PS. There was little variation of absolute rate of cholesterol esterification in the fluid obtained from different sizes of follicles. Fatty acid or triacylglycerol did not participate in the reaction of cholesterol esterification in POFF. No appreciable change in enzymatic activity was found from storing POFF at 4 C for periods of time up to 24 hr or at -70C up to 2 months, but activity was lost thereafter. On the other hand, PS showed a much longer period of stability (5 days at 4 C and 9 months at -70 C). A discrepancy between the fatty acid composition of cholesteryl esters formed by the LCAT reaction and the fatty acid composition at the C-2 position of phosphatidylcholine led the authors to propose a two-step mechanism for the LCAT reaction. It is concluded that the LCAT of POFF, as well as that of plasma, is specific for individual fatty acids than for the fatty acid composition of phosphatidylcholine. The fatty acid concentration of lysophosphatidylcholine decreased during prolonged incubation times (6 to 21 hr) suggesting that the increased lysophosphatidylcholine formed as a product of the LCAT reaction may be reused as substrate for the LCAT reaction or for hydrolysis by lysophosphatidylcholine hydrolase.

Original languageEnglish (US)
Pages (from-to)225-231
Number of pages7
JournalLipids
Volume13
Issue number4
StatePublished - 1978

Fingerprint

Follicular Fluid
follicular fluid
Esterification
esterification
Swine
Cholesterol
cholesterol
swine
Fatty Acids
Fluids
Lysophosphatidylcholines
Phosphatidylcholines
lysophosphatidylcholine
phosphatidylcholines
phosphatidylcholine-choline acyltransferase
Phosphatidylcholine-Sterol O-Acyltransferase
Serum
Chemical analysis
fatty acid composition
fatty acids

ASJC Scopus subject areas

  • Food Science
  • Biochemistry, Genetics and Molecular Biology(all)
  • Biochemistry
  • Cell Biology
  • Organic Chemistry
  • Medicine (miscellaneous)

Cite this

A model for studying LCAT reaction : In vitro cholesterol esterification in pig ovarian follicular fluid. / Yao, J. K.; Chang, S. C S; Ryan, R. J.; Dyck, Peter J.

In: Lipids, Vol. 13, No. 4, 1978, p. 225-231.

Research output: Contribution to journalArticle

Yao, J. K. ; Chang, S. C S ; Ryan, R. J. ; Dyck, Peter J. / A model for studying LCAT reaction : In vitro cholesterol esterification in pig ovarian follicular fluid. In: Lipids. 1978 ; Vol. 13, No. 4. pp. 225-231.
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AB - Phosphatidylcholine acyltransferase (lecithin:cholesterol acyltransferase or LCAT; EC 2.3.1.43) activity was found to be present in pig ovarian follicular fluid (POFF), in addition to pig serum (PS). The cholesterol esterification rate in both POFF and PS is linear with incubation time up to 2 hr. The mean absolute rate of POFF-cholesterol esterification was 8.1 ± 0.4 nmoles per ml per hr approximately one-fourth of that in PS. However, the fractional rate (percent of labeled cholesterol esterified per hr) of POFF-cholesterol esterification was similar to that observed in PS. There was little variation of absolute rate of cholesterol esterification in the fluid obtained from different sizes of follicles. Fatty acid or triacylglycerol did not participate in the reaction of cholesterol esterification in POFF. No appreciable change in enzymatic activity was found from storing POFF at 4 C for periods of time up to 24 hr or at -70C up to 2 months, but activity was lost thereafter. On the other hand, PS showed a much longer period of stability (5 days at 4 C and 9 months at -70 C). A discrepancy between the fatty acid composition of cholesteryl esters formed by the LCAT reaction and the fatty acid composition at the C-2 position of phosphatidylcholine led the authors to propose a two-step mechanism for the LCAT reaction. It is concluded that the LCAT of POFF, as well as that of plasma, is specific for individual fatty acids than for the fatty acid composition of phosphatidylcholine. The fatty acid concentration of lysophosphatidylcholine decreased during prolonged incubation times (6 to 21 hr) suggesting that the increased lysophosphatidylcholine formed as a product of the LCAT reaction may be reused as substrate for the LCAT reaction or for hydrolysis by lysophosphatidylcholine hydrolase.

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