Affinity labels and spectroscopic probes of porcine heart NADP-dependent isocitrate dehydrogenase.
Affinity labels and spectroscopic probes of porcine heart NADP-dependent isocitrate dehydrogenase.
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猪心脏 NADP 依赖性异柠檬酸脱氢酶的亲和标记和光谱探针。
DOI：
10.1042/bst0170307
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发表时间：
1989
影响因子：
3.9
通讯作者：
Colman,RF
中科院分区：
文献类型：
--
作者：
Colman,RF
Porcine heart NADP-dependent isocitrate dehydrogenase (EC 1. l. 1.42) catalyses the oxidative decarboxylation of isocitrate and requires the presence. of divalent metal cations. The active site of this enzyme, while in solution, has been characterized by ultraviolet absorption, 31P and ‘H nmr spectroscopy, fluorescence energy transfer measurements and affinity labelling using coenzyme and substrate analogues with reactive functional groups. The enzyme has a single type of polypeptide chain of molecular mass 58000 kDa (Colman et al., 1970) and under many conditions exists as a dimer of identical subunits (Kelly & Plaut, 198 1). Isocitrate dehydrogenase has a high affinity for the coenzymes NADP and NADPH, while the coenzyme fragments 2 ‘-phosphoadenosine 5’-diphosphoribose (PADPR) and 2’, 5 ‘-adenosine diphosphate (2’, 5’-ADP) have been shown to function as effective competitive inhibitors with respect to NADP (Mas & Colman, 1985). Since the coenzyme fragments lack the nicotinamide and the nicotinamide ribose phosphate moieties, respectively, it is apparent that these portions of the coenzyme are not essential for interaction with the enzyme, although they do contribute to the binding energy. To compare their environments on the enzyme, the difference absorption spectra between isocitrate dehydrogenase-nucleotide complexes and separated enzyme and coenzymes were measured at pH 7.6. The spectral perturbations observed for the enzyme complexes with 2 ‘, 5’-ADP, PADPR and NADP are remarkably similar (Mas & Colman, 1985) suggesting that there are similar interactions
