Respiration, peroxidase, and diphenol oxidase isozymes in reproductive and nonreproductive growth of Glomerella magna

Abstract

Respiration rates were measured and respiratory quotients (RQ) were calculated for sexually reproducing and nonreproducing cultures of Glomerella magna. Oxygen uptake per unit of extractable protein by reproducing cultures was fairly constant until day 7 when it increased markedly as the sexual structures were being differentiated. Oxygen uptake by nonreproducing cultures was highest on days 2, 3, and 4 while initiation of sexual reproduction by exposure to light was still possible. RQ values of reproducing cultures were constant at about 0.85, while the nonreproductive cultures reached a maximum of 1 by day 4 and then declined with culture age to 0.47. The isozymes of peroxidase and o-diphenol oxidase were similar in reproducing and nonreproducing cultures. One "tyrosinase" band and one "laccase" (p-diphenol oxidase) band were observed with tyrosine and p-phenylenediamine as the substrates. Isozymes of peroxidase or diphenol oxidase exhibited different substrate specificities.