Glycine and alanine dehydrogenase activities are catalyzed by the same protein in Mycobacterium smegmatis: upregulation of both activities under microaerophilic adaptation.
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.
Usha
Veeraraghavan
V
AstraZeneca India Pvt Ltd., Malleswaram, Bangalore, India.
Jayaraman
Ramesh
R
Toro
Juan Carlos
JC
Hoffner
Sven E
SE
Das
Kaveri S
KS
D000222:Adaptation, Physiological; D050788:Alanine Dehydrogenase; D000594:Amino Acid Oxidoreductases / Q000096:biosynthesis* / Q000737:chemistry / Q000302:isolation & purification; D000693:Anaerobiosis; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D003470:Culture Media; D004790:Enzyme Induction; D050789:Glycine Dehydrogenase; D020102:Mycobacterium smegmatis / Q000201:enzymology* / Q000254:growth & development / Q000502:physiology; D010100:Oxygen / Q000378:metabolism; D015854:Up-Regulation
D001426:Bacterial Proteins; D003470:Culture Media; D000594:Amino Acid Oxidoreductases; D050788:Alanine Dehydrogenase; D050789:Glycine Dehydrogenase; D010100:Oxygen