ISSN:
1432-072X
Keywords:
Methanobacterium thermoautotrophicum
;
Carbohydrate synthesis
;
Autotrophic CO2 fixation
;
Pyruvate synthase
;
Phosphoenolpyruvate synthetase
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Methanobacterium thermoautotrophicum assimilates CO2 via a novel pathway which involves the synthesis of acetyl CoA from 2 CO2. The pathway of carbohydrate synthesis in this autotroph starting from acetyl CoA and CO2 was studied using, (I) 14CO2 pulse-labeling, (II) [14C]pyruvate long term labelling, and (III) enzyme studies. (I) The distribution of radioactivity incorporated from 14CO2 by an exponentially growing culture during 2 s–120 s incubation periods has been analysed with respect to 3-phosphoglyceric acid and sugar phosphates. Radioactivity first appeared in 3-phosphoglyceric acid and only later in sugar phosphates. Fructose and glucose phosphates were among the earliest labeled carbohydrates followed by pentose phosphates and other sugar phosphates. (II) When the organism was grown in the presence of [2-14C]pyruvate during several generations, radioactivity was incorporated into alanine and glucosamine in a ratio of 1:2. Alanine contained the label at C-2, whilst glucosamine was equally labeled at C-2 and at C-5. (III) The following enzymatic activities were detected in cell extracts with specific activities being sufficiently high to account for the in vivo rate of carbohydrate synthesis: pyruvate synthase, phosphoenolpyruvate synthetase, phosphoenolpyruvate carboxylase, enolase, phosphoglycerate mutase, phosphoglycerate kinase, glyceraldehydephosphate dehydrogenase. The data indicate that glucogenesis from acetyl CoA and CO2 in Methanobacterium involves the pathway depicted in Fig 1.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00413389
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