ศูนย์นวัตกรรมเทคโนโลยีหลังการเก็บเกี่ยว

ATPase activity of mesocarp membranes during postharvest ripening of nectarines.

Heyes, J. A.; Townsend, J. A.;

New Zealand Journal of Crop and Horticultural Science Year: 1992 Vol: 20 Issue: 2 Pages: 125-131 Ref: 26 ref.

1992

บทคัดย่อ

Softening during fruit ripening may be initiated by an increase in proton pumping across the plasma membrane. This would lower the cell wall pH and loosen acid-labile bonds, as well as displacing Ca2+ from load-bearing bonds. The enzyme responsible for proton pumping is the plasma membrane H+-ATPase. The activity of this enzyme in nectarine (cv. Redgold) mesocarp was studied during 4 days of ripening at 20 deg C after harvest at commercial maturity. Fruits began to produce significant amounts of ethylene (>1 micro l kg-1 h-1) from the second day. Flesh firmness began to decline from the third day, but background skin colour did not change until the fourth day. Plasma membranes were extracted from the fruits by phase partitioning. Initial characterization of the H+-ATPase activity showed that it was Mg2+-dependent, K+-stimulated and VO43--sensitive. The Km for MgATP was 0.19 plus or minus 0.02 mM. The Ki value for Ca2+ was estimated at 100 micro M free Ca2+. The in vitro specific activity of the ATPase did not alter significantly during a 4-day period after commercial harvest. There was a slight decline in ATPase activity with increasing ethylene evolution but no significant correlation between ATPase activity and firmness or skin colour.