Phosphorylation of pantothenic acid and pantethine by an enzyme from Proteus morganii.

Before the nature of “bound” pantothenic acid was established, McIlwain and Hughes (1) showed that incubation of pantothenic acid with various streptococci or Proteus morganii led to its “inactivation” as a growth factor for these organisms. This inactivation reaction was dependent upon glycolysis, but independent of growth and the presence of oxygen, and was inhibited by pantoyltaurine (2). McIlwain (3) assumed that both glycolysis and pantothenic acid are necessary for formation of some substance necessary for growth. It now seems probable that this inactivation reaction represented one or more reactions associated with conversion of pantothenic acid to coenzyme A. The latter product and each of the proposed intermediates between it and pantothenic acid are inactive as growth factors for yeast and many bacteri& (4-6). In a previous communication (7) it was stated that one such inactivation reaction in P. morgcznii depended upon the presence of adenosinetriphosphate (ATP) and cysteine, yielding a product identical in behavior to pantothenylcysteine. The latter product, though inactive for most bacteria (5-7), is highly active for Acetobacter suboxydans (5), and appears to be an intermediate in coenzyme A synthesis (5, 7, 8). During this work, acetone-dried cells of P. morganii also were observed to inactivate pantothenic acid as a growth factor for yeast in the absence of cysteine, provided ATP were present. Phosphatase treatment regenerated pantothenic acid inactivated by the cysteine-independent reaction, but not that inactivated by the cysteine-dependent reaction, thus permitting their ready differentiation. The enzyme associated with this cysteine-independent inactivation of pantothenic acid has been obtained in cell-free extracts. Its partial purification and some of its properties are described below.