脱氢抗坏血酸
谷胱甘肽
生物化学
谷胱甘肽还原酶
抗坏血酸
烟草
APX公司
酶
还原酶
过氧化物酶
脱氢酶
化学
生物
分子生物学
谷胱甘肽过氧化物酶
维生素C
食品科学
基因
作者
Maria Concetta de Pinto,Franca Tommasi,Laura De Gara
标识
DOI:10.1016/s0981-9428(00)00773-7
摘要
The ascorbate (ASC) and glutathione (GSH) metabolisms were studied in cultured Nicotiana tabacum cv. Bright Yellow 2 (TBY-2) cells. TBY-2 cells were found to be endowed with L-galactono-γ-lactone dehydrogenase (GLDH) (EC 1.3.2.3), an enzyme that converts L-galactono-γ-lactone into ASC. Cellular fractionation of TBY-2 protoplasts indicated that this enzyme is exclusively localised in mitochondria and associated to the membrane fractions. During the growth cycle of TBY-2 cell culture, GLDH transiently increased, reaching the maximum value on the third day of culture, at the beginning of the exponential phase, when the cell proliferative activity was also higher. Similar behaviour has been observed for ASC and GSH contents. The activities of ascorbate peroxidase (APX) (EC 1.11.1.11), ascorbate-free radical reductase (AFRR) (EC 1.6.5.4), dehydroascorbic acid reductase (DHAR) (EC 1.8.5.1) and glutathione reductase (GR) (EC 1.6.4.2) also transiently raised. However, the scale of the increases varied being about 4-fold for APX and AFRR, 2-fold for DHAR and more than 11-fold for GR. The behaviour of the ASC and GSH recycling enzymes allowed TBY-2 cells to maintain both dehydroascorbic acid and glutathione disulphide at low levels, even under conditions of high ASC and GSH utilisation. The relationship between the ASC and GSH metabolisms during the growth cycle of TBY-2 cell suspension cultures is also discussed.
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