Some properties of the polygalacturonase from four Zimbabwean wild fruits (Uapaca kirkiana, Zizphus mauritiana, Tamarindus indica and Berchemia discolor fruits)

摘要

Polygalacturonase was extracted from ripe Uapaca kirkiana, Zizphus mauritiana, Tamarindus indica and Berchemia discolor fruits of Zimbabwe. Protein concentrations and activities of the enzymes in the extracts were determined in the four fruit extracts, The protein concentrations in the enzyme extracts ranged from 0.82 +-0.17 to 1.97 +-0.13 mg/ml and enzyme activities from 1.99 +-0.13 to 6,64 +-0.38 mmol min~(-1) mg~(-1) in the four fruit extracts. Optimum pH of the enzyme ranged from 4.5 to 5 and optimum tem perature from 25 to 37℃. The enzyme extracts reduced the viscosity of 1% pectin solutions in an experiment which was done together with assay for reducing sugars to prove the activities of the enzyme extracts in the four wild fruits. The K_m and V_(max) ranged from 0.115 to 0.252 mg/ml and 0.0057 to 0.0119 mmol reducing groups/min/mg protein, respectively, in the four polygalacturonase extracts. Calcium chloride and sodium chloride activated the PG from all sources to a greater extend than magnesium chloride and barium chloride. PG from the other three fruits had very little effect on the polysaccharide from U. kirkiana.