Serum protein binding of myoglobin, hemoglobin and hematin.

ECENTLY much attention has been focused on the protein binding of hemoglobin. The hemoglobin binding proteins, collectively called haptoglobin, have been thoroughly studied by several workers.’5 Indentification of these substances has helped to clarify the concept of “renal threshold” for hemoglobin excretion.5’6’9 Subsequently, in an investigation of the difference in “renal threshold” of myoglobin and hemoglobin, Javid et al.’#{176} reported that there was no binding of myoglobin by haptoglobin and in fact could not demonstrate binding of myoglobin by protein. However, later presented evidence of protein binding of myoglobin. This protein-pigment complex was found to have electrophoretic characteristics similar to but not identical with protein bound hemoglobin. In addition, various workers5’8”2”3 have described hemoglobin and hematin binding by a globulin which does not appear to be a haptoglobin. This protein apparently binds the heme portion of the hemoglobin molecule in contrast to haptoglobin which hinds the globin fraction.7 This study was devised to investigate further the binding of heme compounds, especially myoglobin, by human serum proteins.