Premium
Lysophosphatidylcholine acyltransferase activity in Saccharomyces cerevisiae : Regulation by a high‐affinity Zn 2+ binding site
Author(s) -
Richard Martin G.,
McMaster Christopher R.
Publication year - 1998
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/s11745-998-0328-1
Subject(s) - acyltransferase , saccharomyces cerevisiae , phosphatidylcholine , chemistry , lysophosphatidylcholine , enzyme , biochemistry , stereochemistry , substrate (aquarium) , ligand (biochemistry) , enzyme assay , phospholipid , biology , receptor , yeast , membrane , ecology
Saccharomyces cerevisiae cells were demonstrated to contain lysophosphatidylcholine (lysoPtdCho) acyltransferase (E.C. 2.3.1.23) activity. The enzyme displayed K m(app) of 69 μM for lysoPtdCho and 152 μM for oleoyl CoA. Enzyme activity was not affected by the addition of 1 mM Mg 2+ , Mn 2+ , Ca 2− , or 200 mM EDTA. However, Zn 2+ inhibited lysoPtdCho acyltransferase activity to 33% control values at 0.1 mM and to 7% at 1.0 mM Zn 2+ . To further explore the possibility that lysoPtdCho acyltransferase may contain a high‐affinity Zn 2+ binding site, we tested the strong Zn 2+ chelator o ‐phenanthroline for its ability to inhibit enzyme activity. LysoptdCho acyltransferase activity was inhibited to 18 and 27%, respectively, those of control values in the presence of 2 and 1 mM o ‐phenanthroline, implying that a high‐affinity Zn 2+ binding site exists in lysoPtdCho acyltransferase or in an accessory protein that is essential for protein stability and/or activity. Saccharomyces cerevisiae lysoPtdCho acyltransferase activity displayed a broad lysoPtdCho fatty acyl chain substrate specificity utilizing lysoPtdCho molecules ranging in length from C 10 −C 20 (the entire range tested). In addition, the enzyme was capable of using the ether‐linked analog of lysoPtdCho, 1‐ O ‐alkyl‐2‐hydroxy‐ sn ‐3‐glycerophosphocholine, as a substrate. The ability of S. cerevisiae to incorporate radiolabeled 1‐ O ‐alkyl‐2‐hydroxy‐ sn ‐3‐glycerophosphocholine into phosphatidylcholine in vitro was exploited to demonstrate a direct precursor‐product relationship between lysoPtdCho molecules and their incorportation into phosphatidylcholine in vivo . Identical labeling results were obtained in S. cerevisiae cells disrupted for their major transacylase activity, PLB1 , demonstrating that the incorporation of lysolipid was via acyltransferase, and not transacylase, activity.