Hb Providence [β82 (EF 6) Lys→Asn, Asp], Two Forms in Peripheral Blood : The First Case Report in Japan ; Structure, Function and Biosynthesis
Fast-moving abnormal hemoglobins with two types of β chain anomalies were discovered in a Japanese male who lived in Okayama Prefecture. Fingerprinting and amino acid analysis of the abnormal hemoglobins purified by isoelectric focusing revealed displacement of β82 (EF 6) Lys by Asn and Asp. Studies of the biosynthesis of the abnormal hemoglobins in reticulocytes demonstrated production of the β chains (the normal βA plus the abnormal β) in slight excess over the α chain (the normal αA) (non-α/α = 1.33). Furthermore, it was found that the immediate biosynthetic product for the abnormal β chain was β82 (EF 6) Lys→Asn, rather than β82 (EF 6) Lys→Asp. Therefore, the β82 (EF 6) Lys→Asp chain was thought to be the secondary product generated in the circulating blood from β82 (EF 6) Lys→Asn. The abnormal hemoglobins showed slightly increased oxygen affinity (P50 19.2 mmHg, normal control 25.4 mmHg, pH 7.4 at 37 ℃) when they were in the cytosol of erythrocytes, whereas the purified specimens exhibited a decrease in oxygen affinity (Asn type P50 9.43 mmHg, Asp type P50 11.4 mmHg, normal A P50 6.07 mmHg, pH 7.4 at 25℃) and reduced Bohr effect (Asn type 0.332, Asp type 0.269, normal A 0.423). Their oxygen affinity was affected little by addition of the organic phosphates, 2,3-DPG and IHP. Their Hill's n values (2.4 to 2.93) were within the normal range. These findings, including the results of chemical analyses, biosynthetic experiments and oxygen equilibrium studies, are in good agreement with those on Hb Providence Asn and Asp which were reported by Charache et al. and Bonaventura et al. in the United States. This is the first case of Hb Providence discovered in Japan. The functional properties of the two forms of Hb Providence are discussed in comparison with those of Hb Rahere and Hb Helsinki with different substitutions at the same site.
