Pantothenylcysteine, a precursor of pantetheine in Lactobacillus helveticus.

The first evidence concerning 6he origin of the sulfur-containing moiety of pantetheine and CoA’ was the finding in 1952 by Pierpont and Hughes (1) that whole cells of Lactobacillus urabinosus can convert PA t,o CoA only in the presence of cysteine (or cystine). In 1953 Brown and Snell (2) suggested that pantothenylcysteine is an intermediate in the formation of pantetheine from PA and cysteine. This suggestion was based on (a) the apparent enzymatic synthesis of pantothenylcysteine by cell-free extracts of Proteus morgunii, (b) the high activity of this compound in replacing PA for growth of Acetobucter suboxyduns, and (c) the conversion of pantothenylcysteine to pantetheine by dried cells of the latter organism. In 1954 Hoagland and Novelli (3) strengthened the position of pantothenylcysteine as a metabolite by demonstrating that it could substitute for PA and cysteine as substrate for CoA synthesis by dialyzed rat liver extracts. However, the role of pantothenylcysteine in the lactic acid bacteria was uncertain. Brown, Ikawa, and Snell (4) found that, in contrast to its activity for A. suboxyduns, pantothenylcysteine cannot readily replace PA or pantetheine as a growth factor for several species of the lactic group. Pierpont et al. more recently have confirmed these results (5). Of this group of bacteria probably most is known about the growth response of Luctobucillus helveticus to PA and the various bound forms of PA. In short term (20 to 24 hours) growth experiments this bacterium uses pantetheine (or pantethine) about 100 times as effectively as PA, but pantothenylcysteine is only slightly active (4). However, PA becomes increasingly active at lengthened incubation periods (6). The present work was undertaken to clarify the latter result and to study the possible role of pantothenylcysteine in the nutrition and metabolism of L. helveticus. As described below, under the proper conditions both PA and PC are just as active as pantethine even in short term growth experiments. Evidence