Premium
Some characteristics and a comparison 6f the activities of o ‐dihydroxyphenoloxidase activity from five yam ( Dioscorea spp.) species
Author(s) -
Ozo Ozo N.,
Caygill John C.
Publication year - 1985
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2740361012
Subject(s) - dioscorea rotundata , catechol , chemistry , dioscoreaceae , catechin , chlorogenic acid , dioscorea , substrate (aquarium) , chromatography , botany , biochemistry , biology , polyphenol , antioxidant , medicine , alternative medicine , pathology , ecology
o ‐Dihydroxyphenoloxidase (E.C. 1.14.18.1) ( o ‐DPOase) was extracted from acetone‐extracted freeze‐dried yam tubers, and fractionated by (NH 4 ) 2 SO 4 precipitation and chromatography on DEAE‐cellulose to give two forms from Dioscorea alta L. (cv. UM680) and three forms from D. rotundata Poir. (cv. Nwopoke). Polyacrylamide gel electrophoresis revealed one of the forms from each species to contain two protein bands with o ‐DPOase activity. o ‐DPOase from D. alata showed activity with catechol, (+)‐catechin, (−)‐epicatechin and chlorogenic acid, but not with tyrosine, as substrate, o ‐DPOase from D. rotundata showed activity only with catechol and (+)‐catechin. K m values for D. rotundata enzymes, calculated assuming a two‐substrate reaction, were between 0.2 and 0.8 mM for oxygen and 70 and 120 mM for catechol. The enzyme was most active between pH 5.5 and pH 7.0, and showed slight activation after holding for 2 minutes at 40 or 50°C. After heating to above 60°C the enzyme showed evidence of irreversible denaturation. The o ‐DPOase activity extracted from ten cultivars of five species of D. alata L., D. bulbifera L., D. cayenensis Lam., D. dumetorum Pax, and D. rotundata Poir. were compared.