Age-dependent decay of cytochrome b5 and cytochrome b5 reductase in human erythrocytes

Abstract

Age-dependent decrease in cytochrome b5 was observed in erythrocytes from both a normal person and a patient with hereditary methaemoglobinaemia without neurological symptoms. With aging, concentrations of cytochrome b5 in erythrocytes from the patient were almost the same as those in the control. Age-dependent decrease in cytochrome b5 reductase activity in the control erythrocytes was also shown; however, the reductase activity was very low in erythrocytes from the patient over the whole age range. Our studies show that methaemoglobin content of erythrocytes seems to be dependent on the content of cytochrome b5 in the cells, both in the control subject and in the patient.

Efficient Reduction of Vertebrate Cytoglobins by the Cytochrome b5/Cytochrome b5 Reductase/NADH System

“…As many other species, including zebrafish, are known to express CYB5, it seems likely that CYB5 and CYB5R may serve as the physiological reductants of Cygbs not only in humans but in many other species as well. Certainly CYB5 and CYB5R are important to mammalian Hb physiology as defects in both proteins are linked to methemoglobinemia. − Nevertheless, it is also clear that the evolutionary pressure for Hb and Mb reduction is lower than for other putative globin substrates as these proteins have slow autoxidation rates (Table ). Some mammals do have very inefficient reducing systems for Hb; for instance, swine are particularly susceptible to methemoglobinemia due to their low concentrations of CYB5R in RBCs …”

Role of NADPH-Cytochrome P450 Reductase and Cytochrome-b5/NADH-b5Reductase in Variability of CYP3A Activity in Human Liver Microsomes

“…Little is known about the effect of aging and gender on the expression of membrane-bound b 5 and b 5 R. Previous study has shown that b 5 content and b 5 R activity decrease with aging in human erythrocytes (Matsuki et al, 1981). …”

Atividade da NADH-redutase de metemoglobina em hemolisado e membranas eritrocitárias de pacientes hansenianos sob tratamento sulfônico

“…O glóbulo vermelho, durante sua maturação, sofre uma diminuição no número de organelas citoplasmáticas (mitocôndrias, ribossomas) até a ausência total, perdendo, desta forma, a capacidade de repor as enzimas utilizadas para a redução da metemoglobina, formada' quando da ação oxidante exercida pela sulfona. Isto é demonstrado em publicação de autores que encontraram menor atividade enzimática nos eritrócitos mais velhos de pessoas normais e nos pacientes portadores de deficiência da NADH-citocromo-b5-redutase 30 .…”