| Abstract
| - Three isoforms of polyphenol oxidase (PPO) were purified to apparenthomogeneity from the Kewcultivar of Indian pineapple fruit in a four-step procedure. Themajor isoenzyme, with a yield of45%, was found to be a tetramer of identical subunits of molecularmass ≈25 kDa. An ionic strengthdependent association−dissociation equilibrium was observed withpineapple PPO. Amino acidanalysis of the major isoenzyme indicated the presence of a highcontent of glutamic acid, glycine,and serine and a low content of the sulfur-containing amino acids.The enzyme was optimally activebetween pH 6 and 7. The PPO did not show any cresolase activity,and the preferred substrateswere diphenols. Ascorbic acid, l-cysteine, andpotassium metabisulfite were found to be potentinhibitors of PPO. Keywords: Catecholase; pineapple fruit; polyphenol oxidase; PPO-isoenzyme;association−dissociation
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