Latency properties of polyphenol oxidase in two avocado cultivars differing in their rate of browning

Differences in the degree of browning of two cultivars of avocado, Lerman and Fuerte, were investigated by studying the relative activities of buffer‐soluble (“soluble”) and detergent‐soluble (“bound”) forms of the enzyme polyphenoloxidase (PPO). The soluble form was found to exist in a latent as well as an active state. Different isoenzyme patterns were shown to exist for soluble and bound‐PPO as determined by gel electrophoresis and electrofocusing. Sodium dodecylsulphate increased the PPO activity and the protein extracted from the acetone powder without releasing any additional isoenzymes. It did, however, activate latent PPO in the crude and partially purified PPO fractions. The ratios between soluble/bound and between active/latent forms of the PPO enzyme were similar in both avocado cultivars studied. It was therefore concluded that differences in the rate of browning between the two cultivars were accountable more in terms of total and specific activity of PPO rather than in the proportion of the enzyme in bound or latent forms.