Purification and characterization of a Bacillus licheniformis phosphatase specific for D-alpha-glycerophosphate

Bacillus licheniformis ("Ford's type") was found to contain a novel enzyme, D-alpha-glycerophosphatase. The enzyme is highly specific for D-alpha-glycerophosphate, effecting little or no hydrolysis of L-alpha- or beta-glycerophosphate or other similar compounds. All other known alpha-glycerophosphatases preferentially hydrolyze the L isomer. The products of the D-alpha-glycerophosphatase reaction were identified as glycerol and inorganic phosphate. The enzyme is a monomer with an apparent molecular mass of approximately 25 kDa. As with most phosphatases, it requires divalent magnesium for activity, but unlike the nonspecific acid and alkaline phosphatases, its optimum pH is around neutral. Its K(m) for D-alpha-glycerophosphate in the presence of 1 mM Mg2+ was found to be 4.3 mM. D-alpha-glycerophosphatase was produced in B. licheniformis fermentations whether or not high levels of phosphate were present; the same was true of glycerol formation. D-alpha-glycerophosphatase is not strongly inhibited by inorganic phosphate and would therefore be capable of catalyzing the formation of glycerol in the presence of high levels of phosphate. The D-alpha-glycerophosphatase of B. licheniformis is similar in characteristics to L-alpha-glycerophosphatases known to synthesize glycerol in vivo, suggesting that D-alpha-glycerophosphatase may be the final enzyme in the fermentative glycerol formation pathway of B. licheniformis.