Vento R, Giuliano M, Tesoriere L, Tesoriere G
Mol Cell Biochem. 1985 Nov;69(1):27-34. doi: 10.1007/BF00225924.
Amphibian, avian and mammal tissues contain a nucleoside phosphotransferase clearly different from those previously described in vegetables and bacteria. Whatever the animal source, the enzyme showed many similar characteristics as far as substrate specificity, dependence upon Mg2+, instability at 37 degrees C, and the protecting effect of nucleotides were concerned. Moreover, when submitted to gel filtration, the enzyme behaved in all cases as a dissociable high molecular weight protein, whose degree of association was controlled by nucleotides. In amphibian and avian tissues multiple forms of the enzyme seem to be present which differ for the substrate concentration at half-maximal velocity (S0.5); the concentration of nucleotide effector which affords half-maximal protection at 37 degrees C (P0.5); and the Hill coefficient for monophosphate donor. Within each single species, the higher the interaction coefficient was, the lower S0.5 and P0.5 values were. In mammalian tissues one form of nucleoside phosphotransferase seems to prevail where cooperative interactions are almost absent and whose S0.5 as well as P0.5 values do not vary significantly from one tissue to another.
两栖动物、鸟类和哺乳动物的组织中含有一种核苷磷酸转移酶，它与先前在植物和细菌中描述的那些酶明显不同。无论动物来源如何，就底物特异性、对Mg2+的依赖性、在37℃下的不稳定性以及核苷酸的保护作用而言，该酶都表现出许多相似的特性。此外，当进行凝胶过滤时，该酶在所有情况下都表现为一种可解离的高分子量蛋白质，其缔合程度受核苷酸控制。在两栖动物和鸟类组织中似乎存在多种形式的该酶，它们在半数最大速度时的底物浓度（S0.5）、在37℃下提供半数最大保护的核苷酸效应物浓度（P0.5）以及单磷酸供体的希尔系数方面存在差异。在每个单一物种中，相互作用系数越高，S0.5和P0.5值越低。在哺乳动物组织中，一种形式的核苷磷酸转移酶似乎占主导地位，几乎不存在协同相互作用，其S0.5以及P0.5值在不同组织之间没有显著变化。
