Regulation of fermentative metabolism in tomato fruit under low oxygen stress

摘要

Tomato fruit was stored under a continuous flow of 0 percent and 3 percent O_2 (balance N_2) or air for 7 d at 20 deg C to study the regulation of fermentative metabolism. The concentrations of ethanol and acetaldehyde were very low during storage at 3 percent O_2 and air. At 0 percent O_2, ethanol and to a lesser extent acetaldehyde, rapidly accumulated in the tissue. However, lactate concentration did not change during the experiment and was not significantly influenced by O_2 concentration. Pyruvate decarboxylase (PDC) activity greatly increased in fruit exposed to 3 percent O_2, while activity in fruit exposed to 0 percent O_2 was the same level as the control. Alcohol dehydrogenase (ADH) activity greatly increased in fruit exposed to 3 percent, but at 0 percent O_2 was the same level as the control. Lactate dehydrogenase (LDH) activity greatly increased in fruit exposed to 3 percent, but at 0 percent O_2 was the same level as the control. The ADH activity in tomato fruit was about ten timesgreater than that of PDC activity and about 100 times greater than that of LDH activity during storage. Concentration of NADH in fruit exposed to 3 percent O_2 was greater than that in fruit exposed to 0 percent O2 and air. Concentrations of pyruvate didnot change during storage at 1 percent O_2 and air. At 0 percent O_2, pyruvate rapidly accumulated in its tissue. The Km of ADH in tomato fruit was 0.28 mM for acetaldehyde, and 0.058 mM for NADH. The Km of PDC in tomato fruit was 0.38 mM for pyruvate.The Km of LDH in tomato fruit was 0.18 mM for pyruvate. Possible regulation of fermentative metabolism is briefly considered.