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Structure and catalytic mechanism of monodehydroascorbate reductase, MDHAR, from Oryza sativa L. japonica

Cited 7 time in scopus
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Title
Structure and catalytic mechanism of monodehydroascorbate reductase, MDHAR, from Oryza sativa L. japonica
Other Titles
Oryzasativa L. japonica 유래의 monodehydroascorbatereductase 구조와 효소반응 기작
Authors
Park, Ae Kyung
Kim, Han-Woo
Lee, Jun Hyuck
Yoon, Ho-Sung
Yul-Ho Kim
Kim, Young-Saeng
Park, Hyun
Shin, Seung Chul
Roh, Soo Jung
Lee, Chang Woo
Jeon, Byung Wook
Do, Hackwon
Kim, Il-Sup
Keywords
ascobate recycling; ascorbic acid; crystal structure; isoascorbic acid; monodehydroascorbate reductase; reactive oxygen species
Issue Date
2016
Citation
Park, Ae Kyung, et al. 2016. "Structure and catalytic mechanism of monodehydroascorbate reductase, MDHAR, from Oryza sativa L. japonica". SCIENTIFIC REPORTS, 6(33903): 1-10.
Abstract
Ascorbic acid (AsA) maintains redox homeostasis by scavenging reactive oxygen species from prokaryotes to eukaryotes, especially plants. The enzyme monodehydroascorbate reductase (MDHAR) regenerates AsA by catalysing the reduction of monodehydroascorbate, using NADH or NADPH as an electron donor. The detailed recycling mechanism of MDHAR remains unclear due to lack of structural information. Here, we present the crystal structures of MDHAR in the presence of cofactors, nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+), and complexed with AsA as well as its analogue, isoascorbic acid (ISD). The overall structure of MDHAR is similar to other iron-sulphur protein reductases, except for a unique long loop of 63?80 residues, which seems to be essential in forming the active site pocket. From the structural analysis and structure-guided point mutations, we found that the Arg320 residue plays a major substrate binding role, and the Tyr349 residue mediates electron transfer from NAD(P)H to bound substrate via FAD. The enzymatic activity of MDHAR favours NADH as an electron donor over NADPH. Our results show, for the first time, structural insights into this preference. The MDHAR-ISD complex structure revealed an alternative binding conformation of ISD, compared with the MDHAR-AsA complex. This implies a broad substrate (antioxidant) specificity and resulting greater protective ability of MDHAR.
URI
http://repository.kopri.re.kr/handle/201206/7486
DOI
http://dx.doi.org/10.1038/srep33903
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