Isoleucine hemoglobins

All. Allen, D. W., Schroeder, W. A., and Balog, J., Observations on the chromatographic heterogeneity of normal adult and fetal human hemoglobin A study of the effects of crystallization and chromatography on the heterogeneity and isoleucine content. J. Amer. Chem. Soe. 80, 1628-1634 (1958). 

Isoleucine is required for muscle strength and stamina, is used as an energy source for muscle tissue, and is needed to produce hemoglobin. 

Studies of hemoglobin mutants where the nonpolar distal residue jSValEll (—CH(CH3)2) is replaced by alanine (—CH3), isoleucine (—CH(CH3)CH2CH3), and leucine (—CH2CH(CH3)2) reveal that this valine offers steric hindrance to oxygen binding in the T state. 

Insoluble material. This was completely inactive against hemoglobin at pH 2 and Azocoll at pH 5.3. NH2-terminal analysis with dansyl chloride showed both isoleucine and leucine gel electrophoresis at pH 8.1 revealed two bands, one with a mobility similar to that of pepsinogen and the other major band with a mobility intermediate to those of pepsinogen and pepsin. The composition (Table III) is similar to that calculated from the sequence of residues 17-370 in porcine pepsinogen. 

Fig. 5. MS/MS mass spectrum reveals the partial sequence of a ttyptic peptide from the human hemoglobin a subunit This information is sufficient to successfully perform a sequence tag search and identify the protein. L/I stands for leucine or isoleucine, whereas and X denote unknown sequences.

Isoleucine, which is absent in the hemoglobin molecule, can be supplemented to patients with upper gastrointestinal bleeding to restore the balance of amino acids that are taken up by the splanchnic organs. This has been demonstrated to improve mainly protein synthesis in liver and muscle in small observational studies. Prospective randomized clinical trials are, however, still lacking. 

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