TAILIEUCHUNG - Báo cáo khoa học: Endo⁄exo mechanism and processivity of family 18 chitinases produced by Serratia marcescens

We present a comparative study of ChiA, ChiB, and ChiC, the three family 18 chitinases produced bySerratia marcescens. All three enzymes eventu-ally converted chitin to N-acetylglucosamine dimers (GlcNAc2) and a minor fraction of monomers. ChiC differed from ChiA and ChiB in that it initially produced longer oligosaccharides from chitin and had lower activ-ity towards an oligomeric substrate, GlcNAc6. | ềFEBS Journal Endo exo mechanism and processivity of family 18 chitinases produced by Serratia marcescens Svein J. Horn1 Audun S0rbotten2 Bj0rnar Synstad1 Pawel Sikorski2 3 Morten Sdrlie1 Kjell M. Varum2 and Vincent G. H. Eijsink1 1 Department of Chemistry Biotechnology and Food Science the Norwegian University of Life Sciences As Norway 2 NOBIPOL Department of Biotechnology the Norwegian University of Science and Technology Trondheim Norway 3 Biophysics and MedicalTechnology Department of Physics Trondheim Norway Keywords chitinase A chitinase C chitin degradation chitosan degradation processivity Correspondence . Eijsink Department of Chemistry Biotechnology and Food Science The Norwegian University of Life Sciences PO Box 5040 1432 As Norway Tel 47 64965892 Fax 47 64965901 E-mail Website http Received 23 October 2005 accepted 29 November 2005 doi We present a comparative study of ChiA ChiB and ChiC the three family 18 chitinases produced by Serratia marcescens. All three enzymes eventually converted chitin to N-acetylglucosamine dimers GlcNAc2 and a minor fraction of monomers. ChiC differed from ChiA and ChiB in that it initially produced longer oligosaccharides from chitin and had lower activity towards an oligomeric substrate GlcNAc6. ChiA and ChiB could convert GlcNAc6 directly to three dimers whereas ChiC produced equal amounts of tetramers and dimers suggesting that the former two enzymes can act processively. Further insight was obtained by studying degradation of the soluble partly deacetylated chitin-derivative chitosan. Because there exist nonproductive binding modes for this substrate it was possible to discriminate between independent binding events and processive binding events. In reactions with ChiA and ChiB the polymer disappeared very slowly while the initially produced oligomers almost exclusively had even-numbered chain lengths in the 2-12 range. This demonstrates a .

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