ABSTRACT
The specific effects of L-lactate and urate on oxygen binding by the haemo-cyanin of the lobster Homarus vulgaris were investigated. Increasing concentrations of L-lactate were found to increase haemocyanin oxygen-affinity. The relationship between the oxygen affinity (logP50) and [L-lactate] expressed as (AlogP5())(Δlog[L-lactate])−1 was −0.11 at L-lactate concentrations between 0.3 and 11 mmol l−1 and pH7.99±0.03. Urate, likewise, had a potentiating effect on haemocyanin oxygen-affinity: (ΔlogP50)( Δlog[urate])−1 was −0.18 at urate concentrations between 0 and 0.93 mmol l−1 and pH7.99±0.03. Cooperativity, expressed as n50, was reduced by the presence of both modulators.
The influence of the simultaneous presence of both factors on haemocyanin oxygen-affinity was also investigated. The effects of L-lactate and urate on haemocyanin oxygen-affinity were found to be additive. The possible physiological role of these modulators is discussed.
