Microaerophilic adaptation has been described as one of the in vitro dormancy models for
tuberculosis. Studies on Mycobacterium tuberculosis adapted to low
oxygen levels showed an enhancement of
glycine dehydrogenase (deaminating) activity. We studied the physiology of the fast-growing, nonpathogenic strain of Mycobacterium smegmatis ATCC 607 under low
oxygen by shifting the actively growing M. smegmatis cells to static microaerophilic growth conditions. This shifting of M. smegmatis culture resulted in a similar phenomenon as seen with M.
tuberculosis, i.e., elevated
glycine dehydrogenase activity. Further purification of
glycine dehydrogenase from M. smegmatis demonstrated
glyoxylate amination, but failed to demonstrate
glycine deamination, even in the purified fraction. Moreover, the purified
protein showed
pyruvate amination as well as
L-alanine deamination activities. By activity staining, the
protein band positive for
glyoxylate amination demonstrated only
pyruvate amination in the presence of
NAD. Absence of
glycine deamination activity strongly suggested that
alanine dehydrogenase of M. smegmatis was responsible for
glyoxylate amination in the cell lysate. This was further confirmed by demonstrating the similar level of upregulation of both
glyoxylate and
pyruvate amination activities in the cell lysate of the adapted culture.