Atmospheric oxygen level influences alcohol dehydrogenase and pyruvate decarboxylase activities in sweetpotato roots

Document Type

Article

Publication Date

1-1-2002

Abstract

Alcoholic fermentation enzyme activities in sweetpotato (Ipomoea batatas L. Lam, cv. Beauregard) roots varied with atmospheric O2 content (0, 1, 1.5, 5, and 21% O2) at 22 ± 2°C. Pyruvate decarboxylase (PDC) activity and alcohol dehydrogenase (ADH) activity were assayed at their experimentally determined pH optima and increased significantly when roots were placed under anoxic atmospheres (generally ≤1.5 % O2). PDC activity increased more than ADH activity in response to anoxia. PDC activity was 21- to 28-fold less than ADH activity under aerobic conditions, but was 6- to 8-fold less under anoxic atmospheres. Both PDC and ADH activities significantly decreased after transfer from anoxic atmospheres to air. However, PDC activity decreased more rapidly and reached a level similar to aerobic conditions, indicating PDC was more sensitive to oxygen availability than ADH. Generally, PDC and ADH activities continued to increase during the first 4.5 d of low oxygen exposure. PDC activity was strongly correlated to ADH activity during the entire 14.5d exposure period to low oxygen atmospheres. A strong correlation existed between PDC activity and acetaldehyde concentration (R2 = 0.95), but a weak correlation existed between ADH activity and ethanol concentration (R2 = 0.52). Our results explicitly suggest that PDC is likely to be the rate-limiting enzyme in alcoholic fermentation of sweetpotatoes under low oxygen atmospheres.

Publication Source (Journal or Book title)

Journal of Plant Physiology

First Page

129

Last Page

136

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