ISSN:
1432-072X
Schlagwort(e):
Key words Alanine dehydrogenase
;
Ammonia
;
assimilation
;
Mycobacterium
;
Morpholine degradation
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Biologie
Notizen:
Abstract An NAD-dependent, morpholine-stimulated l-alanine dehydrogenase activity was detected in crude extracts from morpholine-, pyrrolidine-, and piperidine-grown cells of Mycobacterium strain HE5. Addition of morpholine to the assay mixture resulted in an up to 4.6-fold increase of l-alanine dehydrogenase activity when l-alanine was supplied at suboptimal concentration. l-Alanine dehydrogenase was purified to near homogeneity using a four-step purification procedure. The native enzyme had a molecular mass of 160 kDa and contained one type of subunit with a molecular mass of 41 kDa, indicating a tetrameric structure. The sequence of 30 N-terminal amino acids was determined and showed a similarity of up to 81% to that of various alanine dehydrogenases. The pH optimum for the oxidative deamination of l-alanine, the only amino acid converted by the enzyme, was determined to be pH 10.1, and apparent K m values for l-alanine and NAD were 1.0 and 0.2 mM, respectively. K m values of 0.6, 0.02, and 72 mM for pyruvate, NADH, and NH4 +, respectively, were estimated at pH 8.7 for the reductive amination reaction.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/s002030050728
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