Characterization of two glutaminases from the filamentous cyanobacterium Anabaena sp. PCC 7120.
The Anabaena genome contains two ORFs that appear to encode glutaminases. The genes were expressed as histidine-tagged fusion proteins in Escherichia coli. The purified proteins possessed glutaminase activity using l-glutamine as the substrate, but differed in biochemical properties. All2934 showed an optimal activity at 20 degrees C and pH 6.0, with a higher affinity for l-glutamine than All4774, which had optimal activity at 37 degrees C and pH 7.5. Remarkably, the glutaminase activity of All2934 was phosphate dependent, while All4774 was phosphate independent. The expression of all2934 and all4774 was analyzed using semi-quantitative reverse transcriptase-PCR. The expression level of all2934 was much higher than that of all4774 under normal and nitrogen-depletion conditions, indicating that All2934 may play an important role in metabolizing glutamine in Anabaena.
Zhou
Jun Xia
JX
Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
Zhou
Jie
J
Yang
Hao Meng
HM
Chen
Mei
M
Huang
Fang
F
D000595:Amino Acid Sequence; D017033:Anabaena / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005972:Glutaminase / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D009584:Nitrogen / Q000378:metabolism; D016415:Sequence Alignment
D001426:Bacterial Proteins; D005972:Glutaminase; D009584:Nitrogen