3-Methylaspartate ammonia-lyase from a facultative anaerobe,strain YG-1002 |
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Authors: | Y Kato Y Asano |
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Institution: | (1) Biotechnology Research Center, Faculty of Engineering, Toyama Prefectural University, Kurokawa 5180, Kosugi, 939-03 Toyama, Japan |
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Abstract: | 3-Methylaspartase was purified 24-fold and crystallized from the crude extract of the cells of a facultative anaerobic bacterium
from soil, strain YG-1002. The molecular mass of the native enzyme was about 84 kDa and that of the subunit was about 42 kDa.
The pH optimum for the deamination reaction of (2S, 3S)-3-methylaspartic acid and those for the amination reaction of mesaconic acid were 9.7 and 8.5; its optimum temperature was
50°C. The enzyme was stable at pH 5.5–11.0 and up to 50°C. The enzyme required both divalent and monovalent cations such as
Mg2+ and K+. The enzyme was inhibited by sulfhydryl reagents, metal-chelating reagents and some divalent cations. The enzyme catalyzed
the reversible amination/deamination reactions between several 3-substituted (S)-aspartic acids and their corresponding fumaric acid derivatives. The enzyme preferentially acted on (2S, 3S)-3-methylaspartic acid and mesaconic acid in the deamination and the amination reactions respectively. The enzyme showed
high similarities in several enzymological properties and N-terminal amino acid sequence with 3-methylaspartase from an obligate
anaerobic bacteriumClostridium tetanomorphum. |
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