Recombinant hemoglobins

Several of the products discussed herein are under intense development. One product, based on recombinant hemoglobin, is in early human trials as of this writing. Other hemoglobin-based solutions are also under review at the EDA. Replacement of red blood cells using massive amounts of protein, free in solution, is an unprecedented therapeutic adventure. 

Studies have shown that in patients with chemotherapy-related anemia, therapy with erythropoietin products (epoetin-alfa and darbepoetin) can increase hemoglobin, decrease transfusion requirements, and improve quality of life.12 Epoetin is recombinant human erythropoietin, and darbepoetin is structurally similar to endogenous erythropoietin. Both bind to the same receptor to stimulate red blood cell production. Darbepoetin differs from epoetin in that it is a glycosylated form and exhibits a longer half-life in the body. The half-lives of a single subcutaneous injection of epoetin or darbepoetin in patients are roughly 27 and 43 hours, respectively. 

B. Kerwin, M. Heller, S. Levin, and T. Randolph, Effect of Tween 80 and sucrose on acute short-term stability and long trem storage at — 20° C of a recombinant hemoglobin, J. Pharm. Sci., 87, 1062 (1998). 

Recombinant hemoglobin, 4 124, 126 Recombinant hepatitis B vaccine, 25 502 Recombinant organisms... 

Preparation of mixed-metal hemoglobin hybrids is achieved by separation of hemoglobin into its constituent a and P chains, followed by demetallation of one of the chains, reconstitution with MP, and chain recombination, yielding the tetrameric [a2(MP), P2(Fe P)] or [a2(Fe P), P2(MP)] species [11]. Thus, MP FeP electron transfer might in principle occur between aj/Pj or ai/P2 subunits. However, the distance between aj and Pj hemes is over 10 A greater than the and P2. This extra distance is expected, and indeed is found, to reduce ET rates by several orders of magnitude. Hence, for all practical purposes we may treat the a2P2 tetramer in terms of two independent [otj, P2] electron transfer complexes. 

Weickert MJ, Pagratis M,Glascock CB, et al. A mutation that improves soluble recombinant hemoglobin accumulation in Escherichia coli in heme excess. Appl Environ Microbiol 1999 65 640. 

Chang TM. Modified hemoglobin-based blood substitutes crosslinked, recombinant and encapsulated hemoglobin. Vox Sang 74(suppl 2) 233, 1998. 

Zuckreman SH, Doyle MP, Gorczynski R, et al. Preclinical biology of recombinant human hemoglobin, rHBl.l. Artif Cells Blood Substit Immobil Biotech-nol 1998 26 231. 

Sakai H, Masada Y, Horinouchi H, et al. Hemoglobin-vesicles suspended in recombinant human serum albumin for resuscitation from hemorrhagic shock in anesthetized rats. Crit Care Med 2004 32 539. 

Although the same transition is expected for the 5-coordinate site in the Ni globins as for 6-coordinate models, ligand release is not observed, presumably, due to rapid geminate recombination in the protein. However, excitation of the 4-coordinate site of Ni hemoglobin does result in transient acquisition of a fifth axial ligand—most likely the proximal histidine. 

The coding sequences of a- and P-globins of human hemoglobin have been fused to the sequence of the chloroplastic transit peptide of the small subunit of Rubisco. These proteins were then coexpressed in transgenic tobacco plants, resulting in the production of a functional form of tetra-meric hemoglobin. The results demonstrate that a complex multimeric protein such as recombinant human hemoglobin can be obtained from tobacco in a functional form. 

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