Activities and multiplicity of phenolase from spinach chloroplasts during leaf ageing

Phenolase activity in spinach leaves homogenates depends on the stage of development of leaves and on the kind of homogenization procedure. Under constant experimental conditions it is low in non-senescent leaves. With the onset of senescence there is a 15–20-fold increase in soluble activity in the supernatants of broken chloroplasts as well as an increase in activation of latent phenolase in fractions containing thylakoids. This rise in activity is due to an increase in particular multiple forms, differing for supernatants and membrane sediments. Phenolase from spinach lacks monophenolase and laccase activities.