ald of Mycobacterium tuberculosis encodes both the alanine dehydrogenase and the putative glycine dehydrogenase.
The putative glycine dehydrogenase of Mycobacterium tuberculosis catalyzes the reductive amination of glyoxylate to glycine but not the reverse reaction. The enzyme was purified and identified as the previously characterized alanine dehydrogenase. The Ald enzyme was expressed in Escherichia coli and had both pyruvate and glyoxylate aminating activities. The gene, ald, was inactivated in M. tuberculosis, which resulted in the loss of all activities. Both enzyme activities were found associated with the cell and were not detected in the extracellular filtrate. By using an anti-Ald antibody, the protein was localized to the cell membrane, with a smaller fraction in the cytosol. None was detected in the extracellular medium. The ald knockout strain grew without alanine or glycine and was able to utilize glycine but not alanine as a nitrogen source. Transcription of ald was induced when alanine was the sole nitrogen source, and higher levels of Ald enzyme were measured. Ald is proposed to have several functions, including ammonium incorporation and alanine breakdown.
Department of Veterans Affairs Medical Center, Long Beach, California, USA.
Michelle M
MM
Giffin
Lucia
L
Modesti
Ronald W
RW
Raab
Lawrence G
LG
Wayne
Charles D
CD
Sohaskey
D000409:Alanine / Q000378:metabolism; D050788:Alanine Dehydrogenase / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D002462:Cell Membrane / Q000737:chemistry; D003001:Cloning, Molecular; D003600:Cytosol / Q000737:chemistry; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D055786:Gene Knockout Techniques; D005998:Glycine / Q000378:metabolism; D050789:Glycine Dehydrogenase / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D006038:Glyoxylates / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics*; D009584:Nitrogen / Q000378:metabolism; D019289:Pyruvic Acid / Q000378:metabolism
D006038:Glyoxylates; D019289:Pyruvic Acid; D050788:Alanine Dehydrogenase; D050789:Glycine Dehydrogenase; C031150:glyoxylic acid; D009584:Nitrogen; D000409:Alanine; D005998:Glycine