Carboxylation of phosphoenolpyruvate by extracts of Neisseria gonorrhoeae.

The enzymatic carboxylation of phosphoenolpyruvate by cell-free extracts of Neisseria gonorrhoeae was examined and determined to be similar to the reaction catalyzed by phosphoenolpyruvate carboxylase (PEPC). This was shown by the irreversibility of the reaction and nucleotide independency. The enzyme was found to have some characteristics different from the other bacterial PEPCs reported. The enzyme showed catalytic activity in the presence of cobalt ions as well as magnesium and manganese ions, was not inhibited by succinate in fresh extracts, and displayed a low Michaelis constant for bicarbonate (0.27 mM), as compared with other PEPCs. The significance of this low Michaelis constant is discussed with respect to the growth of the organism and the importance of this enzyme to protein and nucleic acid synthesis.     

The growth response of the established human cell line, KB, in an acidified medium.

Supplementing Eagle's Minimal Essential Medium with pyruvic acid extended the pH range for maximum growth of KB cells from pH 7.0–7.4 to pH 6.6–7.2. The stimulatory effect of pyruvic acid was independent of pH in the range 6.6–7.2. In contrast to WI-38, KB cells are not adversely effected by the addition of glucose to Eagles Essential Medium containing galactose.