Purification and characterization of two sucrose synthase isoforms from Japanese pear fruit

Plant Cell Physiol. 2000 Apr;41(4):408-14. doi: 10.1093/pcp/41.4.408.

Abstract

Two isoforms (SS I and SS II) of sucrose synthase (SS; EC 2.54.1.13) were purified from Japanese pear fruit and their properties were compared. SS I mainly appeared in young fruit and SS II mainly in mature fruit. SS I and SS II were purified to the specific activity of 3.37 and 4.26 (units (mg protein)(-1)), respectively. The MW of native and subunit proteins of SS I and SS II were almost the same and both SSs seemed to be a tetramer composed of an 83 kDa polypeptide. However, the ionic charges of the native proteins and the kinetic parameters of SSs were different. Specifically, the Km value for UDP-glucose in SS I was the same as that for UDP, while the Km value for UDP-glucose in SS II was less than that for UDP. SS II easily reacted for sucrose synthesis than sucrose cleavage compared with SS I. Therefore, it is considered that SS I and SS II play different roles in the utilization of carbohydrate in young and mature fruit, respectively.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Fruit / enzymology*
  • Glucosyltransferases / isolation & purification*
  • Protein Isoforms / isolation & purification
  • Rosales / enzymology*

Substances

  • Protein Isoforms
  • Glucosyltransferases
  • sucrose synthase