Abstract
We describe a silent and unstable hemoglobin variant, Hb Toranomon, which was discovered by high performance liquid chromatography in an apparently healthy Japanese male during a Hb A1c assay. Isoelec-trofocusing of his hemolysate and chromatographic separation of globin on a CM-cellulose column revealed no abnormality. The isopropanol precipitation test gave a positive result. Amino acid analysis of all peptides isolated from the tryptic digests of the aminoethylated and non-aminoethylated β chain (βA+ βX) by reversed phase high performance liquid chromatography indicated a substitution of Cys → Trp at position 112 of the β chain, which was confirmed by protein sequencing. cDNA sequencing showed the nucleotide sequence of the P112 codon to be TGG instead of TGT, confirming the amino acid substitution described above. The globin biosynthesis ratio (β/α) was 1.00.