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Serine synthesis in cyanobacteria by a nonphotorespiratory pathway
Author(s) -
Colman Brian,
Norman Eric G.
Publication year - 1997
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1997.tb03463.x
Subject(s) - phosphoserine , serine , biochemistry , cyanobacteria , biosynthesis , alanine , biology , enzyme , chemistry , amino acid , bacteria , genetics
The pathway of serine synthesis was investigated in six species of cyanobacteria: Anabaena cylindrica, A. variabilis, A. flos‐aquae, Coccochloris peniocystis, Gleo‐capsa alpicola and Phormidium molle . Activity of the enzymes phosphoglycerate (PGA) dehydrogenase (EC 1.1.1.95), phosphoserine transaminase (EC 2.6.1.52) and phosphoserine phosphatase (EC 3.1.3.3) was detected in vitro in all species, but no PGA phosphatase (EC 3.1.3.20) or hydroxypyruvate reductase (EC 1.1.1.26) activity could be detected. Metabolism of [1‐ 14 C]PGA by cell‐free extracts of C. peniocystis resulted in the labelling of serine, alanine and aspartate, which represented 84, 11 and 4% of the labelled amino acid pool, respectively, Labelled serine isolated from these experiments was 100% carboxyl‐labelled indicating that it was formed directly from PGA. The labelling of serine was markedly reduced by 5 mM phosphoserine. These in vitro findings indicate that cyanobacteria are capable of synthesizing serine directly from PGA, independent of ribulose‐1.5‐bisphosphate oxidation, and that the route of serine synthesis via phosphohydroxypyruvate and phosphoserine is the predominant pathway in these organisms.