Multiple Forms of Phenoloxidase

Abstract

SUMMARY— The phenoloxidase system in the tissues of mushrooms, potatoes, and apples was investigated using a polyacrylamide electrophoretic technique. The enzyme system was shown to exhibit the phenomenon of multiple forms. The multiple form pattern obtained was highly characteristic for each individual species and variety studied, and substrate specificity was evident. The mushroom phenoloxidase system (Agaricus campestris) was shown to consist of at least nine distinct dl‐dopa‐reactive multiple forms, and at least three forms reacting with I‐tyrosine. Potatoes (var. Rural Russet) showed at least 11 bands of dl‐dopa activity, while apples (var. Golden Delicious) had at least three multiple forms of dl‐dopa activity. By introducing the “multiphase” gel electrophoretic technique a better resolution of the multiple forms was obtained. A group of closely related dl‐dopa multiple forms in mushrooms had the unique ability to withstand the temperature of 70°C for one hour. Sulfite, ethylenediamine‐tetraacetic acid (EDTA) and other treatments affected the multiple forms differently. Each multiple form behaved as an individual entity upon repeated elutions and electrophoreses.

Characterisation of ‘Starking’ apple polyphenoloxidase

“…However, PEG (Chung et al 1983 ;Coseteng and Lee 1987), PVP (Walker and Hulme 1966 ;Goodenough and Lea 1979 ;Goodenough et al 1983 ;Choi et al 1987) ; cysteine (Walker and Hulme 1965 ;Chaves and Toma s 1975), and ascorbic acid (Harel et al 1966 ;Constantidines and Bedford 1967 ;JanovitzKlapp et al 1989 ;Zhou et al 1993) are among the compounds that have been used for these purposes in crude enzymatic extracts of apple.…”

Isolation and Characterization of Polyphenol Oxidase Isozymes of Clingstone Peach

“…1; also known as phenolase, phenol oxidase, catechol oxidase, and tyrosinase) is widely distributed in nature. Multiple forms of PPO have been isolated from a wide variety of sources, including mushroom (1,3,10,11,20), apple chloroplasts (8,9), broad bean (19), potato (3,17), Neurospora (5,6), and melanoma (18). The reported number of multiple forms (isozymes) of PPO range from 2 in melanoma to as many as 11 in potato (3).…”

“…Some of the iso- ' (20). The mushroom PPO system was reported to consist of nine DL-DOPAreactive PPOs, but only three of these PPOs were found to have activity toward L-tyrosine (3). Peaches were reported to contain at least three PPO isozymes with activity toward DL-DOPA (3).…”

Polyphenol oxidase in wild rice (Zizania palustris)

“…The relatively lower stability of the wild rice enzyme may be related to its relatively lower optimum temperature and might be an important factor modulating the curing of wild rice with respect to curing temperature regimen. Although it is not known why such heterogeneity exists, it has been speculated that multiple enzyme forms might provide greater resistance to substrate or product inhibition (Constantinides and Bedford, 1967). Six protein bands were observed but only four of them showed PPO activity when the gels were soaked in catechol solution (Figure 4b).…”