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B6db references: 76039469

type Journal Article
authors Inatomi, K.; Slaughter, J. C.
title Glutamate decarboxylase from barley embryos and roots. General properties and the occurrence of three enzymic forms
journal Biochem J
ui 76039469
year (1975)
volume 147
number 3
pages 479-84.
keywords Alcohol Oxidoreductases/analysis
abstract Glutamate decarboxylase in extracts of barley has a Km value for L- glutamate of 22 mM and is activated by the addition of pyridoxal phosphate by up to 3.5 times. Sucrose-density-gradient experiments indicate the presence of two enzyme forms with molecular weights 256000 and 120000. The lower-molecular-weight form appears to be relatively inactive and spontaneously associates to the higher-molecular-weight form on storage. The enzyme is inhibited by thiol reagents and the distribution of activity on density gradients is altered in favour of the lower-molecular-weight form by the presence of 2-mercaptoethanol. After removal of the 2-mercaptoethanol spontaneous association to the higher-molecular-weight form occurs. The presence of oxygen in the extraction buffer and in the water during imbibition leads to a relative increase in the higher-molecular-weight form compared with situations where oxygen is excluded. In contrast, glutamate decarboxylase in extracts of 3-day-old barley roots has a Km value for L-glutamate of 3.1 mM and is activated up to 10% by addition of pyridoxal phosphate. The root enzyme occurs as a single species with molecular weight 310000 and this is unaffected by 2-mercaptoethanol although thiol reagents do act as weak inhibitors. The molecular weight is also unaffected by the presence or absence of oxygen in the extraction buffers.
last changed 2002/11/12 16:17

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