Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0392674 (exhaustion)
 13,658 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Gluconate which was produced in cultures of Aspergillus niger with glucose as the sole source of carbon, or which was added after exhaustion of glucose, was utilized by this mold. In cell-free extracts from gluconate degrading mycelia gluconokinase and five enzymes of the pentose phosphate pathway were identified. Enzymes of the Entner-Doudoroff pathway and of a modified (non-phosphorylating) Entner-Doudoroff system, as well as a gluconate dehydrogenase could not be detected. It is concluded that gluconate after its phosphorylation to 6-phosphogluconate is metabolized via the pentose phosphate pathway by the strain used.
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PMID:Utilization of gluconate by Aspergillus niger. I. Enzymes of phosphorylating and nonphosphorylating pathways. 407 56

The catalytic activity of ribulosebisphosphate carboxylase (Rubisco) declined as soon as catalysis was initiated by exposure to its substrate, d-ribulose-1,5-bisphosphate (ribulose-P(2)). The decline continued exponentially, with a half-time of approximately 7 minutes until, eventually, a steady state level of activity was reached which could be as low as 15% of the initial activity. The ratio of the steady state activity to the initial activity was lower at low CO(2) concentration and at low pH. The inhibitors 6-phosphogluconate and H(2)O(2) alleviated the inactivation, increasing the final/initial rate ratio and the half-time. Varying ribulose-P(2) concentration in the range above that required to saturate catalysis did not affect the kinetics of inactivation. The affinities for CO(2) and ribulose-P(2) were unaffected by the inactivation. The decline in activity occurred with preparations of ribulose-P(2) which contained no detectable d-xylulose-1,5-bisphosphate and also with ribulose-P(2) which had been generated enzymatically immediately before use. Inclusion of an aldolase system for removing d-xylulose-1,5-bisphosphate also did not alter the inactivation process. The inactivated Rubisco did not recover after complete exhaustion of ribulose-P(2). We conclude that the inactivation is not caused by readily-reversible binding of ribulose-P(2) at a site different from the active site and that it is unlikely to be attributable to inhibitory contaminants in ribulose-P(2) preparations.
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PMID:A Kinetic Characterization of Slow Inactivation of Ribulosebisphosphate Carboxylase during Catalysis. 1666 28