Substrate activity of phosphonic acid analogues of CDPdiglyceride in the synthesis of phosphoglycerides in Escherichia coli.

Two phosphonic acid analogues of CDPdiglyceride, D L-2-hexadecoxy-3-octadecoxypropylphosphonyl-O-(cytidine 5'-phosphate) (analogue (I), and D L-3,4-dioctadecoxybutylphosphonyl-O-(cytidine 5'-phosphate) (analogue (II), have been synthesized and examined as substrates for the enzymes involved in the synthesis of phosphoglycerides in Escherichia coli. Both compounds were substrates for CDPdiglyceride:sn-glycerol-3-phosphate phosphatidyl transferase. The analogues had similar Km values (Km of 0.060 mM for analogue (II): Km of 0.080 mM for analogue (I) and a V identical to that of CDPdipalmitin (Km of 0.044 mM). In contrast, the analogues were poor substrates for CDPdiglyceride:L-serine phosphatidyl transferase. The analogues had lower Km values (Km of 0.40 mM for analogue (II); Km of 0.80 mM for analogue (I) than CDPdipalmitin (Km of 1.4 mM). The V, although identical for both analogues, was ten-fold lower than that observed with the natural substrate. An analysis of the products of these enzymatic reactions suggests that phosphatidylglycerophosphate phosphatase and phosphatidylserine decarboxylase may also possess a certain degree of substrate specificity.