Flamigni F, Marmiroli S, Caldarera C M, Guarnieri C
Dipartimento di Biochimica, Università di Bologna, Italy.
Biochem J. 1989 Apr 1;259(1):111-5. doi: 10.1042/bj2590111.
Ornithine decarboxylase (ODC), an enzyme with 'essential' thiol group(s), may be inactivated in vitro by removal of thiol reducing agents and re-activated by soluble factors from rat liver in the presence of NADPH or GSH. The NADPH- and GSH-dependent reducing systems were separated and resolved into three components, called factors A, B1 and B2, by chromatographic techniques. Factor B1 (Mr 12,000) could reactivate ODC in the presence of GSH and co-purified with thiol transferase activity. Factor B2 (Mr 12,000) and factor A (Mr approx. 110,000) were both needed to re-activate ODC in the presence of NADPH, and co-purified with thioredoxin and thioredoxin reductase activity respectively. In an attempt to investigate the physiological role of the 'essential' thiol group(s) of ODC, erythroleukaemia cells were incubated with NN-bis-(2-chloroethyl)-N'-nitrosourea, t-butyl hydroperoxide and vinblastine, which are known to increase the cellular GSSG/GSH ratio, azelaic acid, an inhibitor of thioredoxin reductase, and sodium arsenite, a strong inhibitor of the ODC-re-activating factors. All these compounds were able to decrease significantly the ODC activity induced in these cells. These results suggest that the thiol transferase- and thioredoxin-dependent systems may be physiologically relevant in maintaining ODC in the active, reduced, state.
鸟氨酸脱羧酶（ODC）是一种含有“必需”巯基的酶，在体外，去除巯基还原剂可使其失活，在存在烟酰胺腺嘌呤二核苷酸磷酸（NADPH）或谷胱甘肽（GSH）的情况下，大鼠肝脏中的可溶性因子可使其重新激活。通过色谱技术将依赖NADPH和GSH的还原系统分离并解析为三个组分，称为因子A、B1和B2。因子B1（分子量12,000）在存在GSH的情况下可使ODC重新激活，并与巯基转移酶活性共纯化。因子B2（分子量12,000）和因子A（分子量约110,000）在存在NADPH的情况下均需要用于使ODC重新激活，并且分别与硫氧还蛋白和硫氧还蛋白还原酶活性共纯化。为了研究ODC“必需”巯基的生理作用，将红白血病细胞与已知会增加细胞氧化型谷胱甘肽/还原型谷胱甘肽（GSSG/GSH）比值的N，N-双（2-氯乙基）-N'-亚硝基脲、叔丁基过氧化氢和长春碱、硫氧还蛋白还原酶抑制剂壬二酸以及ODC重新激活因子的强抑制剂亚砷酸钠一起孵育。所有这些化合物均能够显著降低这些细胞中诱导的ODC活性。这些结果表明，巯基转移酶和硫氧还蛋白依赖性系统在生理上可能与维持ODC处于活性、还原状态相关。
