Allosteric Modulation of Haemocyanin Oxygen- Affinity by L-lactate and Urate in the Lobster Homarus Vulgaris I. Specific and Additive Effects on Haemocyanin Oxygen- Affinity
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چکیده
The specific effects of L-lactate and urate on oxygen binding by the haemocyanin 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 (Alog/5())(Alog[L-lactate])"' was -0.11 at L-lactate concentrations between 0.3 and 1 Immoir' and pH7.99±0.03. Urate, likewise, had a potentiating effect on haemocyanin oxygen-affinity: (AlogP50)(Alog[urate])~ L was -0.18 at urate concentrations between 0 and O^mmoir and pH7.99±0.03. Cooperativity, expressed as «50, 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.
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Binding of Urate and Caffeine to Hemocyanin Analyzed by Isothermal Titration Calorimetry
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