PHOSPHORYLATION LINKED TO ASCORBATE OXIDATION IN MYCOBACTERIUM PHLEI

Evidence for a site of phosphorylation between cytochrome c and oxygen in Mycobacterium phlei was presented. The segment of the respiratory chain was isolated by use of a NHQNO block which acted at the level of cytochrome b and by use of ascorbate-TPD as the substrate. Evidence has been obtained which indicated that electrons from ascorbate via TPD entered the respiratory chain at the level of cytochrome c and that electrons from endogenous substrates were not participating in the reaction. Phosphate esterification with ascorbate-TPD required the presence of the supernatant fraction in addition to the particulate fraction. Oxidation of ascorbate proceeded at a negligible rate unless mediated by a high potential electron donor such as TPD. Low concentrations of this agent were sufficient to catalyze electron transfer from ascorbate to cytochrome c, while higher concentrations of TPD stimulated a shunt around the NHQNO block. With most preparations, the TPD shunt required the addition of a substrate, such as succinate, to generate electrons. In addition, the NHQNO was a better inhibitor of succinate-linked respiration than was the oxidation observed with the NAD+-linked pathway. © 1969.