f Further Observations on Carbohydrate Metabolism and its Regulation in Azotobacter beijerinckii
- Authors: Michael P. Stephenson*, Frank A. Jackson†, Edwin A. Dawes
- First Published Online: 01 November 1978, Microbiology 109: 89-96, doi: 10.1099/00221287-109-1-89
- Subject: Biochemistry
- Issue Published:
SUMMARY: Certain enzymes of glucose catabolism in Azotobacter beijerinckii were studied and their activities in steady-state chemostat cultures were measured under various nutrient limitations. 2-Keto-3-deoxy-6-phosphogluconate aldolase was separated from 6-phosphogluconate dehydratase by affinity chromatography and the previously observed inhibition of the Entner-Doudoroff enzymes by tricarboxylic acids and ATP was attributed to chelation of Mn2+ and Mg2+ which activate the dehydratase. Glucose-6-phosphate dehydrogenase was unaffected by phosphoenolpyruvate while fructose-1,6-bisphosphate aldolase was activated by Co2+, K+ or NH4 + ions. Transketolase, transaldolase and triosephosphate isomerase were present but previous reports of 6-phosphogluconate dehydrogenase activity were shown to be artefacts. The findings confirm the major role of the Entner-Doudoroff pathway in glucose catabolism in A. beijerinckii. Pyruvate dehydrogenase, a key enzyme for carbon entry to the tricarboxylic acid cycle and to poly-β-hydroxybutyrate synthesis, was inhibited by acetyl-coenzyme A and NADH.
Present address: Cyanamid of Great Britain Ltd, Fareham Road, Gosport, Hants PO13 OAS.
Present address: Forensic Science Laboratory, Shakespeare Street, Nottingham NG1 4FR.
© Society for General Microbiology, 1978 | Published by the Microbiology Society
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