Partial Purification of Gibberellin Oxidases from Spinach Leaves

Abstract
Four enzyme activities catalyzing the following oxidative steps in the gibberellin (GA) biosynthetic pathway have been extracted from spinach (Spinacia oleracea L.) leaves after exposure to 8 long days: GA12 .fwdarw. GA53 .fwdarw. GA44 .fwdarw. GA19 .fwdarw. GA20. Two of these, GA53 oxidase and GA19 oxidase, were separable from the other two, GA44 oxidase and GA12 13-hydroxylase, by anion exchange high performance liquid chromatography (HPLC). Apparent molecular weights of the four enzymes as determined by gel filtration HPLC are: GA12 13-hydroxylase, 28,400; GA53 oxidase, 42,500; GA44 oxidase, 38,100; GA19 oxidase, 39,500. GA44 oxidase was purified approximately 100-fold in 0.3% yield by a combination of ammonium sulfate fractionation, anion exchange HPLC, phenyl-Sepharose chromatography and gel filtration HPLC.