Absorption spectra of erythrocyte hemolysate from a normal subject, the
Hemoglobin (Hb1) M Saskatoon patient and the
Hb M Boston patients were investigated. Difference spectrum between the hemolysate from either freshly obtained or 37 degrees C-incubated blood of the
Hb M Saskatoon patient and that of the normal blood suggested that about 50% of the abnormal chain were in the ferrous state in the patient's blood. In contrast, no abnormal chain containing the ferrous
heme was detected in the hemolysate from the fresh blood of the
Hb M Boston patient. Resonance Raman (RR) studies indicated that
methemoglobin (metHb) M Saskatoon with a weak Fe-tyrosinate interaction contained the six-coordinate
heme like normal
metHb A whereas metHb M Boston had the five-coordinate
heme. Studies on effects of pH on absorption and RR spectra of these three
hemoglobins suggested that the coordinated tyrosinate in the abnormal chain of
Hb M Saskatoon was dissociated at pH 5.0. This unique
heme structure of
Hb M Saskatoon may relate to the susceptibility for the reduction by erythrocyte
methemoglobin reductases, which is responsible for mild
cyanosis of
Hb M Saskatoon disease.