tailieunhanh - Báo cáo khoa học: Donor and acceptor substrate selectivity among plant glycoside hydrolase family 32 enzymes

Plant family 32 glycoside hydrolase enzymes include hydrolases (cell wall invertases, fructan exohydrolases, vacuolar invertases) and fructosyltrans-ferases. These enzymes are very similar at the molecular and structural levels but are functionally different. Understanding the basis of the func-tional diversity in this family is a challenging task. | REVIEW ARTICLE Donor and acceptor substrate selectivity among plant glycoside hydrolase family 32 enzymes Wim Van den Ende1 Willem Lammens1 2 Andre Van Laere1 Lindsey Schroeven1 and Katrien Le Roy1 1 Laboratory for Molecular Plant Physiology Heverlee Belgium 2 Laboratory for Biocrystallography Leuven Belgium Keywords fructan fructosyl transferase invertase structure-function sucrose Correspondence W. Van den Ende Laboratory for Molecular Plant Physiology Kasteelpark Arenberg 31 B-3001 Leuven-Heverlee Belgium Fax 32 16321967 Tel 32 16321952 E-mail Received 18 June 2009 revised 7 August 2009 accepted 19 August 2009 doi Plant family 32 glycoside hydrolase enzymes include hydrolases cell wall invertases fructan exohydrolases vacuolar invertases and fructosyltrans-ferases. These enzymes are very similar at the molecular and structural levels but are functionally different. Understanding the basis of the functional diversity in this family is a challenging task. By combining structural and site-directed mutagenesis data Asp239 in AtcwINV1 was identified as an amino acid critical for binding and stabilizing sucrose. Plant fructan exohydrolases lack such an Asp239 equivalent. Substitution of Asp239 led to the loss of invertase activity while its introduction in fructan exohydrolases increased invertase activity. Some fructan exohydrolases are inhibited by sucrose. The difference between the inhibitor fructan exohydrolase and the substrate invertase binding configurations of sucrose can be explained by the different orientation of Trp82. Furthermore the evolutionary hydro-lase transferase transition could be mimicked and the difference between S-type fructosyltransferases sucrose as donor and F-type fructosyltransfe-rases fructan as donor could be unravelled. Introduction Fructans are polymers of fructose Fru and an extension of sucrose Suc and they occur in many plant species .