Herzfeld A, Mezl V A, Knox W E
Biochem J. 1977 Jul 15;166(1):95-103. doi: 10.1042/bj1660095.
The direction and capacity for the metabolism of delta1-pyrroline-5-carboxylate in a number of rat tissues ere investigated by measuring the activities of delta1-pyrroline-5-carboxylate reductase, delta1-pyrroline-5-carboxylate dehydrogenase and proline oxidase. Each of these enzymes catalyzed unidirectional reactions in which delta1-pyrroline-5-carboxylate was either the substrate or product. Delta1-Pyrroline-5-carboxylate reductase activities that were much higher than any previously reported were obtained by avoiding its inactivation in the cold. delta1-Pyrroline-5-carboxylate dehydrogenase, previously said to act on both D- and L-isomers of delta1-pyrroline-5-carboxylate, acted only on the L-isomer. Proline oxidase could not be measured in two adult tissues, in which an inhibitor appeared after birth. The activity of delta1-pyrroline-5-carboxylate reductase significantly paralleled that of ornithine aminotransferase in 23 tissues, showing a widespread potential for proline synthesis from ornithine. An independently distributed potential in fewer tissues for proline degradation to alpha-oxoglutarate was shown by the significantly similar tissue distributions of proline oxidase. Delta1-pyrroline-5-carboxylate dehydrogenase and glutamate dehydrogenase. Reverse metabolism of glutamate or proline to ornithine would be atypical in rat tissues with these distributions of unidirectional enzyme reactions.
通过测量δ1-吡咯啉-5-羧酸还原酶、δ1-吡咯啉-5-羧酸脱氢酶和脯氨酸氧化酶的活性,研究了多种大鼠组织中δ1-吡咯啉-5-羧酸的代谢方向和能力。这些酶各自催化单向反应,其中δ1-吡咯啉-5-羧酸要么是底物,要么是产物。通过避免其在低温下失活,获得了比以往任何报道都高得多的δ1-吡咯啉-5-羧酸还原酶活性。δ1-吡咯啉-5-羧酸脱氢酶,以前认为对δ1-吡咯啉-5-羧酸的D型和L型异构体都起作用,实际上只作用于L型异构体。在两个成年组织中无法测量脯氨酸氧化酶,在这两个组织中出生后出现了一种抑制剂。在23种组织中,δ1-吡咯啉-5-羧酸还原酶的活性与鸟氨酸转氨酶的活性显著平行,表明从鸟氨酸合成脯氨酸具有广泛的潜力。脯氨酸氧化酶、δ1-吡咯啉-5-羧酸脱氢酶和谷氨酸脱氢酶在较少组织中的组织分布显著相似,表明在较少组织中存在将脯氨酸降解为α-酮戊二酸的独立分布的潜力。在具有这些单向酶反应分布的大鼠组织中,谷氨酸或脯氨酸逆向代谢为鸟氨酸将是非典型的。