REVERSIBLE EFFECT OF BICARBONATE ON THE INHIBITION OF MYCOBACTERIAL AND YEAST TRANSGLUCOSYLASES BY MYCORIBNIN.

Lornitzo, Frank A. (Veterans Administration Hospital, Madison, Wis.), and Dexter S. Goldman. Reversible effect of bicarbonate on the inhibition of mycobacterial and yeast transglucosylases by mycoribnin. J. Bacteriol. 89:1086-1091. 1965.-The transglucosylase which catalyzes the formation of trehalose-6-phosphate from uridine diphosphate (UDP)-glucose and glucose-6-phosphate was purified from cell-free extracts of Mycobacterium tuberculosis H37Ra. During the purification procedure, the transglucosylase loses its sensitivity to mycoribnin, an inhibitor also found in these extracts. Sensitivity of the transglucosylase to mycoribnin is regained when the bicarbonate concentration of either enzyme or mycoribnin preparations is reduced to about 0.01 mm; sensitivity to mycoribnin is lost when low concentrations (< 1 mm) of bicarbonate are present in the reaction mixture. Transglucosylase preparations retain their bicarbonate-induced insensitivity to mycoribnin after dilution to a bicarbonate concentration which is ineffective for the initial conversion to insensitivity. The transglucosylases of brewer's yeast and of physiologically young (9-day) H37Ra cells, previously reported as insensitive to mycoribnin, have been partially purified. If bicarbonate is excluded from these preparations, the transglucosylases become sensitive to mycoribnin; bicarbonate abolishes this sensitivity. The H37Ra transglucosylase is specific for UDP-glucose and glucose-6-phosphate as substrates. UDP-galactose does not serve as a glycosyl donor; galactose-6-phosphate, ribose-5-phosphate, and glucose-1-phosphate do not act as glucosyl acceptors. Oligoribonucleotide analogues of mycoribnin do not inhibit substantially the H37Ra transglucosylase.