3s6t
Crystal Structure of insect beta-N-acetyl-D-hexosaminidase OfHex1 V327G complexed with PUGNAc
Structural highlights
FunctionHEXC_OSTFU Hydrolyzes one beta-GlcNAc unit at a time from the non-reducing ends of substrates, with a preference for shorter substrates. The 2-acetamido group and the beta-glycoside bond linkage in the substrate are required for its activity. Active with p-nitrophenyl (pNP)-beta-GlcNAc, pNP-beta-GalNAc and chitooligosaccharides (degree of polymerization from 2 to 6), but not with the complex N-glycan substrate (GlcNAcbeta-1,2Manalpha-1,6)(GlcNAcbeta-1,2Manalpha-1,3)Manbeta-1,4GlcNAcbeta-1,4GlcNAc-PA (GnGn-PA), pNP-alpha-GlcNAc or with the long polymer colloidal chitin. Involved in chitin catabolism (PubMed:18959754). Involved in the degradation of old cuticle during the pupation stage (PubMed:21106526).[1] [2] Publication Abstract from PubMedChitinolytic beta-N-acetyl-D-hexosaminidase is a branch of GH20 beta-N-acetyl-D-hexosaminidase that is only distributed in insects and microorganisms, and is therefore a potential target for the action of insecticides. O-(2-acetamido-2-deoxy-D-glucopyransylidene)-amino-N-phenylcarbamate (PUGNAc) was initially identified as an inhibitor against GH20 beta-N-acetyl-D-hexosaminidases. So far no crystal structure of PUGNAc in complex with any GH20 beta-N-acetyl-D-hexosaminidase has been reported. We showed here the sensitivities of chitinolytic beta-N-acetyl-D-hexosaminidases towards PUGNAc can vary in 100 folds, with the order being OfHex1 (insect beta-N-acetyl-D-hexosaminidase from Ostrinia furnacalis)< SmCHB (bacterial chitobiase from Serratia marcescens)< SpHex (bacterial beta-N-acetyl-D-hexosaminidase from Streptomyces plicatus). To explain this difference, the crystal structures of wide-type OfHex1 as well as mutant OfHex1 (V327G) in complex with PUGNAc were determined at 2.0-A and 2.3-A resolutions and aligned with the complex structures of SpHex and SmCHB. The result showed that the sensitivities of these enzymes to PUGNAc was dedicated by the active pocket size, with OfHex1 having the largest but with the narrowest entrance, while SpHex having the smallest, suitable for holding the inhibitor, whereas that of SmCHB having the widest entrance. By widening the size of the active pocket entrance of OfHex1 through replacing active site Val327 with Gly, sensitivity of OfHex1 to PUGNAc became similar to that of SmCHB. The structural differences among chitinolytic beta-N-acetyl-D-hexosaminidases leading to different sensitivities to PUGNAc may be useful for developing species-specific pesticides and bactericides. Active-pocket size differentiating insectile from bacterial chitinolytic beta-N-acetyl-D-hexosaminidases.,Liu T, Zhang H, Liu F, Chen L, Shen X, Yang Q Biochem J. 2011 Jun 21. PMID:21692744[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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