ISSN:
1432-136X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary 1. The pH dependence ofOctopus dofleini hemocyanin oxygenation is so great that below pH 7.0 the molecule does not become fully oxygenated, even in pure O2 at 1 atm pressure. However, the curves describing percent oxygenation as a function of $$P_{O_2 } $$ appear to be gradually increasing in oxygen saturation, rather than leveling out at less than full saturation. Hill plots indicate that at pH 6.6 and below the molecule is stabilized in its low affinity conformation. Thus, the low saturation of this hemocyanin in air is due to the very large Bohr shift, and not to the disabling of one or more functionally distinct O2 binding sites on the native molecule. 2. Experiments in which pH was monitored continuously while oxygenation was manipulated in the presence of CO2 provide no evidence of O2 linked binding of CO2. While CO2 does influence O2 affinity independently of pH, its effect may be due to high levels of HCO 3 − and CO 3 − , rather than molecular CO2, and it may entail a lowering of the activities of the allosteric effectors Mg2+ and Ca2+.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00692562
