In vivo studies on stereospecificity of the monoglyceride kinase, lysophosphatidic acid acyltransferase, phosphatidic acid phosphatase and CDP-diglyceride synthase of Streptococcus mutans BHT using the stereoisomers of the ether lipid, dodecylglycerol

Abstract

Streptococcus mutans BHT metabolizes radioactive 3-dodecyl- sn-glycerol (sn-3-DDG) almost exclusively to lysophosphatidic acid, phosphatidic acid and 1,3-diradyl- sn-glycerol, whereas the cells of this organism metabolize 1-dodecyl- sn-glycerol ( sn-1- DDG) to all of the glycerol lipids of S. mutans BHT, with the largest amounts incorporated into phosphatidylglycerol and diradylglycerol (mostly the 1,2- but also the 1,3-isomer). (The common names of lipids, such as phosphatidic acid, are used in the broader sense to mean that the lipid may contain alkyl as well as acyl groups.) The addition of an equivalent amount of nonradioactive sn-3- DDG to radioactive sn-1- DDG causes more of the radioactivity to accumulate at phosphatidic acid. These results indicate that the monoglyceride kinase (EC 2.7.1.94), lysophosphatidic acid acyltransferase (EC 2.3.1.40) and the monoglyceride acyltransferase (EC 2.3.1.22) enzymatic reactions are not stereospecific, and that the CDP-diglyceride synthase (EC 2.7.7.41) and phosphatidic acid phosphatase (EC 3.1.3.4) metabolic steps are stereospecific in S. mutans BHT. The synthesis of phosphatidic acid and lysophosphatidic acid from sn-3-DDG provides a unique method for synthesizing these glycerol lipids with the uncommon stereochemical configuration in which the phosphate moiety is in the sn-1 position.