His-404 and His-405 are Essential for Enzyme Catalytic Activities of a Bacterial Indole-3-Acetyl-l-Aspartic Acid Hydrolase.
In: Plant & Cell Physiology, Jg. 45 (2004-09-01), Heft 9, S. 1335-1341
academicJournal
Zugriff:
Bacterial indole-3-acetyl-l-aspartic acid (IAA-Asp) hydrolase has shown very high substrate specificity compared with similar IAA-amino acid hydrolase enzymes found in Arabidopsis thaliana. The IAA-Asp hydrolase also exhibits, relative to the Arabidopsis thaliana-derived enzymes, a very high Vmax (fast reaction rate) and a higher Km (lower substrate affinity). These two characteristics indicate that there are fundamental differences in the catalytic activity between this bacterial enzyme and the Arabidopsis enzymes. By employing a computer simulation approach, a catalytic residue, His-385, from a non-sequence-related zinc-dependent exopeptidase of Pseudomonas was found to structurally match His-405 of IAA-Asp hydrolase. The His-405 residue is conserved in all related sequences of bacteria and Arabidopsis. Point mutation experiments of this His-405 to seven different amino acids resulted in complete elimination of enzyme activity. However, point mutation on the neighboring His-404 to eight other residues resulted in reduction, to various degrees, of enzyme activity. Amino acid substitutions for His-404 also showed that this residue influenced the minor activity of the IAA-Asp hydrolase for the substrates IAA-Gly, IAA-Ala, IAA-Ser, IAA-Glu and IAA-Asn. These results show the value and potential of structural modeling for predicting target residues for further study and for directing bioengineering of enzyme structure and function. [ABSTRACT FROM AUTHOR]
Titel: |
His-404 and His-405 are Essential for Enzyme Catalytic Activities of a Bacterial Indole-3-Acetyl-l-Aspartic Acid Hydrolase.
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Autor/in / Beteiligte Person: | Chou, Jyh-Ching ; Welch, William H. ; Cohen, Jerry D. |
Zeitschrift: | Plant & Cell Physiology, Jg. 45 (2004-09-01), Heft 9, S. 1335-1341 |
Veröffentlichung: | 2004 |
Medientyp: | academicJournal |
ISSN: | 0032-0781 (print) |
DOI: | 10.1093/pcp/pch153 |
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