Sanna Maria T, Olianas Alessandra, Castagnola Massimo, Sollai Luigi, Manconi Barbara, Salvadori Susanna, Giardina Bruno, Pellegrini Mariagiuseppina
Department of Sciences Applied to Biosystems, University of Cagliari, Cittadella Universitaria, Monserrato I-09042, CA, Italy.
Comp Biochem Physiol B Biochem Mol Biol. 2004 Oct;139(2):261-8. doi: 10.1016/j.cbpc.2004.08.005.
The oxygen-binding properties of hexameric hemocyanin (Hc) from Scyllarides latus were investigated with respect to pH, temperature, and modulating effect exerted by calcium, lactate, and urate. The oxygen affinity decreased at higher temperature, was slightly affected by pH, and was insensitive to lactate. Nevertheless, urate markedly increased Hc-oxygen affinity and its temperature sensitivity, acting as the physiological major positive effector: four urate sites per hexamer with an overall affinity constant of 1 x 10(4) M(-1) were found and the exothermic contribution of their binding was found to be about 30 kJ mol(-1). Calcium ions largely influenced oxygen affinity: their effect, which has an opposite sign at low (0-1 mM) and high (0.1-1 M) concentration ranges, indicates the presence of two independent types of binding sites with high and low affinity, respectively; however, only the former ones seem to be operative in vivo because, at physiological calcium concentrations, they are already saturated and the oxygen affinity is reduced.
研究了宽突软甲藻六聚体血蓝蛋白（Hc）在pH值、温度以及钙、乳酸盐和尿酸盐所产生的调节作用方面的氧结合特性。在较高温度下氧亲和力降低，受pH值影响较小，对乳酸盐不敏感。然而，尿酸盐显著提高了Hc的氧亲和力及其温度敏感性，作为生理上主要的正效应物：发现每个六聚体有四个尿酸盐结合位点，总亲和常数为1×10⁴ M⁻¹，并且发现其结合的放热贡献约为30 kJ mol⁻¹。钙离子对氧亲和力有很大影响：它们在低浓度（0 - 1 mM）和高浓度（0.1 - 1 M）范围内的作用具有相反的符号，表明分别存在高亲和力和低亲和力的两种独立类型的结合位点；然而，似乎只有前者在体内起作用，因为在生理钙浓度下，它们已经饱和，氧亲和力降低。
