Effects of allylisothiocyanate (an inhibitor of ethylene action) on ethylene-enhancement of chlorophyllase in satsuma mandarin (Citrus unshiu) fruit were investigated. The aim is to accumulate knowledge of action mechanism of ethylene. The isothiocyanate inhibited ethylene-enhancement of chlorophyllase activity in vivo. A correlation (r=0.9580, significant at 0.1% level) exists between chlorophyllase activity and Hunter's color index, (L+ b) /2+a, a marker of degreening. Participation of 'chlorophyllide a peroxidase', a candidate enzyme of degreening, was recognized, in independent of ethylene and/or allyl-isothiocyanate treatments. It is conclusive that chlorophyllase is a key enzyme in ethylene-enhanced chlorophyll degradation of satsuma mandarin fruit.
