Oxygen affinities (p50) of myoglobins from four vertebrate species (Canis familiaris, rattus norvegicus, mus musculus and Gallus domesticus) as determined by a kinetic and an equilibrium method

Abstract Rate constants of the reaction with oxygen of myoglobins from four vertebrate species ( Canis familiaris, Rattus norvegicus, Mus musculus and Gallus domesticus ) and the isolated α A and β A chains of human adult hemoglobin (HbA) were determined by the stopped-flow-spectrophotomeric method. Half-saturation oxygen pressure ( P 50 ) of the proteins calculated from the rate constants, assuming a simple bimolecular reaction model, agreed very well with those directly determined by oxygen equilibria. The proteins used were freshly prepared, and fully characterized by electrophoretic and ultracentrifugal analyses. Sulphydryl groups in the Hb chains were ascertained to be completely regenerated.