Role of the glutamate 332 residue in the transglycosylation activity of Thermus maltogenic amylase

Tae Jip Kim, Cheon Seok Park, Hee Yeon Cho, Sun Shin Cha, Jeong Sun Kim, Soo Bok Lee, Tae Wha Moon, Jung Wan Kim, Byung Ha Oh, Kwan Hwa Park

Research output: Contribution to journalArticlepeer-review

34 Citations (Scopus)

Abstract

A sequence alignment shows that residue 332 is conserved as glutamate in maltogenic amylases (MAases) and in other related enzymes such as cyclodextrinase and neopullulanase, while the corresponding position is conserved as histidine in α-amylases. We analyzed the role of Glu332 in the hydrolysis and the transglycosylation activity of Thermus MAase (ThMA) by site-directed mutagenesis. Replacing Glu332 with histidine reduced transglycosylation activity significantly, but enhanced hydrolysis activity on α-(1,3)-, α-(1,4)-, and α-(1,6)-glycosidic bonds relative to the wild- type (WT) enzyme. The mutant Glu332Asp had catalytic properties similar to those of the WT enzyme, but the mutant Glu332Gln resulted in significantly decreased transglycosylation activity. These results suggest that an acidic side chain at position 332 of MAase plays an important role in the formation and accumulation of transfer products by modulating the relative rates of hydrolysis and transglycosylation. From the structure, we propose that an acidic side chain at position 332, which is located in a pocket, is involved in aligning the acceptor molecule to compete with water molecules in the nucleophilic attack of the glycosyl-enzyme intermediate.

Original languageEnglish
Pages (from-to)6773-6780
Number of pages8
JournalBiochemistry
Volume39
Issue number23
DOIs
Publication statusPublished - 2000 Jun 13

All Science Journal Classification (ASJC) codes

  • Biochemistry

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