LATENCY PROPERTIES OF POLYPHENOL OXIDASE IN 2 AVOCADO CULTIVARS DIFFERING IN THEIR RATE OF BROWNING

Differences in the degree of browning of 2 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) [EC 1.10.8.1]. The soluble form existed in a latent and an active state. Different isoenzyme patterns existed for soluble and bound-PPO as determined by gel electrophoresis and electrofocusing. Sodium dodecylsulfate increased the PPO activity and the protein extracted from the acetone powder without releasing any additional isoenzymes. It did 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. Differences in the rate of browning between the 2 cultivars were apparently accountable more in terms of total and specific activity of PPO rather than in the proportion of the enzyme in bound or latent forms.