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De karakterisatie van het phenylalanine-dehydrogenase van Nocardia SP. 239

Rijssel, M. van (1987) De karakterisatie van het phenylalanine-dehydrogenase van Nocardia SP. 239. Master's Thesis / Essay, Biology.

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The inducable catabole enzyme L—phenylalanine dehydrogenase of Nocardia sp 239 was found to be a NAD dependend enzyme, which katalyses the following reaction: L—phe + NAD <==> NADH + NH4 + phenylpyruvate. The pK of this reaction was 17.5, indicating the equillibrium of the reaction to be on the aminoacid side. Parahydroxy—phenylpyruvate turned out to be also a substrate for the enzyme, in contrast to D—phenylalanine. The L—phenylalanine dehydrogenase is a monomer of 42000 Dalton, with a temperature optimum of 50 C and an optimum pH of 10 for the aminating reaction. The enzyme could be induced by no aminoacid other than L— or D—phenyl—alanine. Growth rate and specific activity were higher by growth on D—phenylalanine than on L—phenylalanine. The enzymes induced by L—ph or D—phe were comparable in affinity, size and behaviour. Therefore a racemase is postulated for growth on D—phenylalanine. Co factor regeneration with alcohol—dehydrogenase (AdH) was possible but because of instabillity of both the AdH and L—phedH the productionrate of L—phenylalanine was limited being 5 g/l.h. Conversion of phenylpyruvate was 96%. Maximum activity of the partially purified enzyme was found to be 7.5 umol/mg.min.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Biology
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 07:47
Last Modified: 15 Feb 2018 07:47

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