Effect of temperature on the stereoselectivity of phospholipase D toward glycerol in the transphosphatidylation of phosphatidylcholine to phosphatidylglycerol.

In this study, the effect of temperature on the stereoselectivity of phospholipase D (PLD) toward the two primary hydroxyl groups of glycerol in the transphosphatidylation reaction of phosphatidylcholine to phosphatidylglycerol (PtdGro) was investigated. For this purpose, PLD from bacteria (Streptomyces septatus TH-2, S. halstedii subsp. scabies K6, and Actinomadura sp.) and cabbage were tested. At the reaction temperatures employed (0-60 degrees C), the proportions of the two PtdGro diastereomers, namely, 1,2-dioleoyl-sn-glycero-3-phospho-3'-sn-glycerol (R,R configuration) and 1 ,2-dioleoyl-sn-glycero-3-phospho-1'-sn-glycerol (R,S configuration), which were produced with PLD from Streptomyces TH-2 and Actinomadura sp., changed gradually from 50% R,R and 50% R,S at 50-60 degrees C to 70% R,R and 30% R,S at 0 degrees C. These alterations suggested that the stereoselectivity of the bacterial PLD toward the two primary hydroxyl groups of prochiral glycerol was significantly influenced by reaction temperature. PLD from Streptomyces K6 showed relatively little effect of temperature on stereoselectivity, giving 65-69% R,R in the temperature range of 60-10 degrees C examined. The plots of In ([R,R]/[R,S]) vs. 1/T gave good linear fits for these three bacterial PLD. No temperature effect was observed for cabbage PLD, which gave an almost equimolar mixture of the R,R and R,S diastereomers in the range from 0 to 40 degrees C. The temperature-dependent change in enantiomeric selectivity of the bacterial PLD promises potentially profitable commercial exploitation.