Effect of thiol reagents on functional properties and heme oxidation in the hemoglobin of Geochelone carbonaria.
The reaction of thiol reagents with G. carbonaria hemoglobin was studied, and the oxygen equilibrium and kinetic of oxidation of derivatives determined. The oxygen affinity and kinetic of oxidation of hemoglobin derivatives were modified to various extents depending on the nature of thiol reagents used. Diamide yielded approximately 80% polymeric hemoglobin, although the oxidation kinetic, and the functional properties, were practically invariant (T1/2 = 10.0 min.; P50 = 5.0 mm Hg at pH 7.4; alkaline Bohr effect = -0.64). Iodoacetamide did not modify the electrophoretic pattern significantly, although all the free SH groups of hemoglobin were alkylated. A P50 of 2.5 mmHg at pH 7.4 and the Bohr effect of -0.15 were obtained; the T1/2 of about 6.4 min. was shorter than that for un-modified Hb. Similar T1/2 were obtained for Hb treated with oxidized glutathione, which produced polymeric Hb and glutathionyl-Hb. The oxygen binding characteristics showed that both of Hb derivatives, glutathionyl-Hb and polymeric Hb, maintain the capacity to transport the gas.
Departamento de Bioquímica, IB, Universidade Estadual de Campinas, SP, Brazil.
M A
MA
Torsoni
R I
RI
Viana
B F
BF
Barros
G
G
Stoppa
M
M
Cesquini
S H
SH
Ogo
D000818:Animals; D003958:Diamide / Q000494:pharmacology; D005978:Glutathione / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D019803:Glutathione Disulfide; D006418:Heme / Q000378:metabolism*; D006454:Hemoglobins / Q000187:drug effects / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007460:Iodoacetamide / Q000494:pharmacology; D007700:Kinetics; D046911:Macromolecular Substances; D010084:Oxidation-Reduction; D010108:Oxyhemoglobins / Q000187:drug effects / Q000378:metabolism*; D013439:Sulfhydryl Reagents / Q000494:pharmacology*; D014426:Turtles
D006454:Hemoglobins; D046911:Macromolecular Substances; D010108:Oxyhemoglobins; D013439:Sulfhydryl Reagents; D003958:Diamide; D006418:Heme; D005978:Glutathione; D019803:Glutathione Disulfide; D007460:Iodoacetamide