TY - JOUR
T1 - The γ-aminobutyric acid shunt contributes to closing the tricarboxylic acid cycle in Synechocystis sp. PCC 6803
AU - Xiong, Wei
AU - Brune, Daniel
AU - Vermaas, Willem
N1 - Publisher Copyright:
© 2014 John Wiley & Sons Ltd.
PY - 2014/8/1
Y1 - 2014/8/1
N2 - A traditional 2-oxoglutarate dehydrogenase complex is missing in the cyanobacterial tricarboxylic acid cycle. To determine pathways that convert 2-oxoglutarate into succinate in the cyanobacterium Synechocystis sp. PCC 6803, a series of mutant strains, Δsll1981, Δslr0370, Δslr1022 and combinations thereof, deficient in 2-oxoglutarate decarboxylase (Sll1981), succinate semialdehyde dehydrogenase (Slr0370), and/or in γ-aminobutyrate metabolism (Slr1022) were constructed. Like in Pseudomonas aeruginosa, N-acetylornithine aminotransferase, encoded by slr1022, was shown to also function as γ-aminobutyrate aminotransferase, catalysing γ-aminobutyrate conversion to succinic semialdehyde. As succinic semialdehyde dehydrogenase converts succinic semialdehyde to succinate, an intact γ-aminobutyrate shunt is present in Synechocystis. The Δsll1981 strain, lacking 2-oxoglutarate decarboxylase, exhibited a succinate level that was 60% of that in wild type. However, the succinate level in the Δslr1022 and Δslr0370 strains and the Δsll1981/Δslr1022 and Δsll1981/Δslr0370 double mutants was reduced to 20-40% of that in wild type, suggesting that the γ-aminobutyrate shunt has a larger impact on metabolite flux to succinate than the pathway via 2-oxoglutarate decarboxylase. 13C-stable isotope analysis indicated that the γ-aminobutyrate shunt catalysed conversion of glutamate to succinate. Independent of the 2-oxoglutarate decarboxylase bypass, the γ-aminobutyrate shunt is a major contributor to flux from 2-oxoglutarate and glutamate to succinate in Synechocystis sp. PCC 6803.
AB - A traditional 2-oxoglutarate dehydrogenase complex is missing in the cyanobacterial tricarboxylic acid cycle. To determine pathways that convert 2-oxoglutarate into succinate in the cyanobacterium Synechocystis sp. PCC 6803, a series of mutant strains, Δsll1981, Δslr0370, Δslr1022 and combinations thereof, deficient in 2-oxoglutarate decarboxylase (Sll1981), succinate semialdehyde dehydrogenase (Slr0370), and/or in γ-aminobutyrate metabolism (Slr1022) were constructed. Like in Pseudomonas aeruginosa, N-acetylornithine aminotransferase, encoded by slr1022, was shown to also function as γ-aminobutyrate aminotransferase, catalysing γ-aminobutyrate conversion to succinic semialdehyde. As succinic semialdehyde dehydrogenase converts succinic semialdehyde to succinate, an intact γ-aminobutyrate shunt is present in Synechocystis. The Δsll1981 strain, lacking 2-oxoglutarate decarboxylase, exhibited a succinate level that was 60% of that in wild type. However, the succinate level in the Δslr1022 and Δslr0370 strains and the Δsll1981/Δslr1022 and Δsll1981/Δslr0370 double mutants was reduced to 20-40% of that in wild type, suggesting that the γ-aminobutyrate shunt has a larger impact on metabolite flux to succinate than the pathway via 2-oxoglutarate decarboxylase. 13C-stable isotope analysis indicated that the γ-aminobutyrate shunt catalysed conversion of glutamate to succinate. Independent of the 2-oxoglutarate decarboxylase bypass, the γ-aminobutyrate shunt is a major contributor to flux from 2-oxoglutarate and glutamate to succinate in Synechocystis sp. PCC 6803.
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U2 - 10.1111/mmi.12699
DO - 10.1111/mmi.12699
M3 - Article
C2 - 24989231
AN - SCOPUS:84918792766
SN - 0950-382X
VL - 93
SP - 786
EP - 796
JO - Molecular Microbiology
JF - Molecular Microbiology
IS - 4
ER -