Characterization of acetyl-CoA and propionyl-CoA carboxylases encoded by Leptospira interrogans serovar Lai: an initial biochemical study for leptospiral gluconeogenesis via anaplerotic CO(2) assimilation.
Leptospira interrogans is the causative agent of leptospirosis. The in vitro growth of L. interrogans requires CO(2) and a partial 3-hydroxypropionate pathway involving two acyl-CoA carboxylases was suggested by genomic analysis to assimilate CO(2). Either set of the candidate genes heterologously co-expressed in Escherichia coli was able to demonstrate both acetyl-CoA carboxylase (ACC) and propionyl-CoA carboxylase (PCC) activities. The tri-subunit holoenzyme (LA_2736-LA_2735 and LA_3803), although failed to be purified, was designated ACC based on its substrate preference toward acetyl-CoA. The partially purified bi-subunit holoenzyme (LA_2432-LA_2433) has a considerably higher activity against propionyl-CoA as the substrate than that of acetyl-CoA, and thus, designated PCC. Native polyacrylamide gel electrophoresis indicated that this PCC has a molecular mass of around 669 kDa, suggesting an α(4)β(4) quaternary structure and both structural homology modeling and site-directed mutagenesis analysis of its carboxyltransferase subunit (LA_2433) indicated that the A431 residue located at the bottom of the putative substrate binding pocket may play an important role in substrate specificity determination. Both transcriptomic and proteomic data indicated that enzymes involved in the suggested partial 3-hydroxypropionate pathway were expressed in vivo in addition to ACC/PCC and the homologous genes in genomes of other Leptospira species were re-annotated accordingly. However, as the in vitro detected specific activity of ACC in the crude cell extract was too low to account for the growth of the bacterium in Ellinghausen-McCullough-Johnson-Harris minimal medium, further systematic analysis is required to unveil the mechanism of gluconeogenesis via anaplerotic CO(2) assimilation in Leptospira species.
Key Laboratory of Synthetic Biology,  Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032,  China.
Nanqiu
N
Peng
Yi
Y
Zhong
Qing
Q
Zhang
Mingyue
M
Zheng
Wei
W
Zhao
Hualiang
H
Jiang
Chen
C
Yang
Xiaokui
X
Guo
Guoping
G
Zhao
D000595:Amino Acid Sequence; D002245:Carbon Dioxide / Q000737:chemistry; D019735:Carbon-Carbon Ligases / Q000737:chemistry*; D004926:Escherichia coli / Q000378:metabolism; D005943:Gluconeogenesis; D007700:Kinetics; D007921:Leptospira interrogans / Q000378:metabolism*; D007922:Leptospirosis; D013058:Mass Spectrometry / Q000379:methods; D043586:Methylmalonyl-CoA Decarboxylase / Q000737:chemistry*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D011487:Protein Conformation; D040901:Proteomics / Q000379:methods; D017386:Sequence Homology, Amino Acid
D002245:Carbon Dioxide; D019735:Carbon-Carbon Ligases; C018757:acyl-CoA carboxylase; D043586:Methylmalonyl-CoA Decarboxylase