Isoelectric Focusing Evidence for Banana Isoenzymes with Mono and Diphenolase Activity

Abstract

Isoelectric focusing on thin layers of Sephadex G-75 superfine gel followed by the print technique was used to investigate the presence of polyphenol oxidase isoenzymes in banana fruits. The enzyme preparation from pulp tissues of unripe "Dwarf Cavendish" bananas, partially purified by (NH&SO, fractionation, revealed 14 isoenzymes having both monophenolase (p-cresol substrate) and diphenolase (dopamine or catechol substrate) functions with isoelectric points (~1) in the pH range 45.5.Similarly, two strains of the cv "Red Skin" showed 10 and 13 isoenzymes with pI in the pH range 4-5.8, most of which were capable of hydroxylation of monophenols. Individual isoenzymes exhibited variations in their activity towards mono and odiphenols.

Banana Polyphenol Oxidase: Occurrence and Change of Polyphenol Oxidase Activity in Some Banana Cultivars during Fruit Development

“…These PPOs had fairly weak and/or no activity towards such trihydroxybenzenes as pyrogallol, gallic acid, and phloroglucinol. Similar substrate specificities of PPO had been found in other banana cultivars (Palmer, 1963;Galeazzi & Sgabieri, 1981;Thomas & Janave, 1986;Yang et al, 2000;. These results indicated that all banana pulp PPOs tested had both tyrosinase and o-diphenolase activities as reported by Thomas and Janave (1986).…”

“…PPO has been widely studied in many fruits and vegetables to prevent the browning which results in the loss of their marketability (Kahn, 1977;Park et al, 1980;Park & Luh, 1985;Augustin et al, 1985;Tono et al, 1986;Fujita & Tono, 1979;Fujita & Tono, 1988;Fujita et al, 1991;Murata et al, 1992;Chilaka et al, 1993;Fujita et al, 1995;Castaner et al, 1996;Fujita et al, 1997;Ding et al, 1998). The PPO in banana (Musa sapientum L.) had been characterized (Palmer, 1963;Galeazzi & Sgabieri, 1981;Thomas & Janave, 1986;Yang et al, 2000;Yang et al, 2001), because a remarkable browning occurred in the pulp section. Many banana cultivars which fall into several genome groups are being cultivated in the world, however, little is known about the occurrence of PPO in them or on the change of PPO activity during development of the fruit.…”

Profile of peroxidase isoforms influenced by spongy tissue disorder in Alphonso mango (Mangifera indica L.) fruits

“…Small filter paper strips of the gel width were moistened with the electrode solutions, and placed at the cathode and anode ends of the gel. The electrodes were placed on these strips adjacent to the gel, and small filter paper strips were connected to the electrode reservoir solutions (Thomas and Janave 1986). After pre-focusing at 100 V for 30 min, the protein samples (*20 lg in 0.01-0.025 cm 3 ) were loaded in the cavities, and electrofocusing was run for 3 h at 500 V, followed by 1 h at 800 V. The POX bands were visualized as detailed in the native PAGE.…”

“…Horizontal IEF was carried out in a Desaga Thin-layer Isoelectric focusing chamber, maintained at 4-6°C (Thomas and Janave 1986), in 10% polyacrylamide gels containing 5% ampholytes (Pharmacia), in the pI range 2-11. The gels were prepared by gluing 3 9 2 9 1 mm (l 9 w 9 h) pieces of polypropylene pieces in the center of one glass plate, and then 2.0 mm polyacrylamide gels containing ampholytes were prepared.…”

Influence of abscisic acid on polyphenol oxidase browning potential in avocado

“…Earlier work (Scriven & Wills, 1984) linked ABA to storage breakdown in apples. The objective of this study was to investigate the effect of ABA on levels of the browning enzyme polyphenol oxidase (PPO) and hence final fruit quality (Kahn, 1975;Thomas & Janave, 1986) for early and later-harvested fruit.…”