Portal de Periódicos da CAPES

Trypsin-catalyzed synthesis of peptide bond in human hemoglobin. Oxygen binding characteristics of Gly-NH2(142 alpha) Hb.

1982; Elsevier BV; Volume: 257; Issue: 4 Linguagem: Inglês

10.1016/s0021-9258(19)68082-8

1083-351X

Kiyoshi Nagai, Yasunori Enoki, Susumu Tomita, Takanori Teshima,

Electron Spin Resonance Studies

Incubation of human hemoglobin (Hb) A with glycineamide (Gly-NH2) in the presence of trypsin gives rise to two bands of approximately equal amount on the isoelectric focusing gel.Structural analyses, including digestion with trypsin and carboxypeptidases A and B, have shown that one is unmodified Hb A and the other is Gly-NH~(142a) Hb in which Gly-NH, is bound to the COOH-terminal residue of the a subunit (Arg 141a) via peptide bond.Gly-NHz(142a) H b exhibits slightly increased affinity for oxygen and slightly reduced heme-heme interaction as compared with normal Hb A. Although Gly-NH2( 1424 Hb exhibits normal 2,3diphosphoglycerate effect, the alkaline Bohr effect and chloride effect are diminished.These oxygen binding properties are attributable to abolished binding of chloride to the anion binding site positioned between the a-amino group of Val l a and the guanidinium group of Arg 141a.Gly-NH2(142a) Hb restores normal oxygen binding properties upon trypsin digestion which removes Gly-NH2 from the COOH terminus of the a sub-