Faster heme loss from hemoglobin E than HbS, in acidic pH: Effect of aminophospholipids.

We report studies on loss of heme at or below pH 3.0 from two clinically important hemoglobin variants, HbE and HbS, in the presence and absence of phopholipid membranes. The kinetics of heme loss has been studied at pH 3.0 to simulate the same at a faster rate than at physiological pH, for spectroscopic investigation. Results obtained from the study clearly establish the probable fate of the lost heme to partition into the phospholipid bilayer independent of the pH range. This is also of particular importance to membranes containing the aminophospholipid and cholesterol which are predominantly localized in the inner leaflet of erythrocytes. Absorption measurements indicated such loss of heme when the Soret peak at 415 nm blue-shifted to 380 nm at pH 3.0. The extent of this blue shift decreased from 35 nm to ~15 nm in the presence of small unilammelar vesicles of both dimyristoyl- and dioleoyl-based phosphatidylcholine and phosphatidylethanolamine, indicating partitioning of the released heme in the membrane bilayer. The kinetics of heme loss was faster from HbE than HbA and HbS, obeying first-order reaction kinetics. Released heme could be involved in the premature destruction of erythrocytes in hemoglobin disorders.

Hemoglobin Yamagata: Hemoglobin Variant Detected by HbA1c Test / 대한진단검사의학회지

Hemoglobin (Hb) Yamagata is a rare Hb variant, which has been reported only twice-one case each in Japan and Korea. This variant arises from a Lys --> Asn substitution due to a mutation of AAA to AAC or AAT at codon 133 of the beta-globin gene. This study reports the third case of a patient detected with Hb Yamagata [HBB: c.399A>T; p.Lys133Asn] and discusses the effect of this variant on HbA1c measurement. This variant was detected in a 70-yr-old Korean man with diabetes mellitus during a routine follow-up. The HbA1c concentration determined using Variant ll Turbo (Bio-Rad, USA) was abnormally high at 47.9%. It was impossible to measure the HbA1c level accurately using Variant ll Thalassemia Mode (Bio-Rad, USA). However, the HbA1c levels analyzed by HLC-723 G7 (Tosoh, Japan), Cobas Integra (Roche, Switzerland) and NycoCard (Axis-Shield, Norway) were 5.0%, 8.0%, and 7.9%, respectively. This study shows that Hb Yamagata interferes with the accurate measurement of HbA1c levels in a diabetic patient. Taking these findings into consideration, we think that an immunoassay or affinity chromatography can be used as an alternate method for measuring the HbA1c level in a patient with this variant. In conclusion, a patient can be inferred to have an Hb variant if the HbA1c concentration is abnormally high or low or if there is a discrepancy between the results obtained using different methods, and if the clinical status of the patient suggests the presence of abnormal Hb. Subsequently, the HbA1c values can be determined by methods based on different principles.