| Project/Area Number |
03680175
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
代謝生物化学
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| Research Institution | KUMAMOTO UNIVERSITY |
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Principal Investigator |
TANASE Sumio KUMAMOTO UNIVERSITY, SCHOOL OF MEDICINE, ASSISTANT PROFESSOR, 医学部, 助教授 (20112401)
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| Co-Investigator(Kenkyū-buntansha) |
HIGAKI Tsuyosi KUMAMOTO UNIVERSITY COLLEGE OF MEDICAL SCIENCE, RESEARCH ASSISTANT, 医療技術短期大学部, 助手 (70128304)
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| Project Period (FY) |
1991 – 1992
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| Project Status |
Completed (Fiscal Year 1992)
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| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1992: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1991: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Keywords | Aspartic acid / Aminotransferase / Pyridoxal / Catalytic activity / Enzyme structure / Genetic engineering / Amino acid substitution / Induced fit / アスパラギン酸アミノ基転移酵素 / ピリドキサ-ルりん酸 / サブユニット間相互作用 |
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| Research Abstract |
Porcine cytosolic aspartate aminotransferase is composed of two identical subunits of 412 residues. Each subunit consists of three domains ; an aminoterminal segment (residues 1-14), a small domain (residues 15-49 and 326-412) and a large domain (residues 50-325). X-ray studies indicated that the amino-terminal region may involve in the subunit interaction and His68 is located within a distance of strong hydrogen bonding with the residues of neighboring subunit. In the present study, the functional role of some amino acid residues in the subunit interaction were probed by applying the site-directed in vitro mutation technique for amino acid substitutions.
(1) Deletion of amino-terminal residues revealed that an amino-terminal region is particularly important for the maintenance of structural integrity as well as the correct movement of the small domain that is closely related to substrate binding and catalysis.
(2) Substitution of His68 suggested that the strong counter ionic interaction with residues of neighboring subunit may contribute to intersubunit interaction and to maintenance of a rigid and proper structure of the enzyme.
(3) Limited proteolysis experiment of His68 mutant showed that deletion of aminoterminal region of the mutant enzyme resulted in a little decrease of catalytic activity as compared with the case of wild-type enzyme. Gel filtration study indicated that monomeric structure of truncated His68 mutant enzyme. However, truncated enzyme showed very week stability to heat and pH change.
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