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Background The aim of the present work was to characterize the molecular defects of a slow-migrating (albumin Zagreb) and a fast-migrating (albumin Krapina) genetic variant of human serum albumin detected in heterozygous persons living in Croatia and to elucidate the fatty acid-binding properties of the two alloalbumins. Methods Purification and structural identification of the variants were performed by conventional protein chemistry methods, whereas types and amounts of albumin-bound, endogenous fatty acids were determined by gas chromatography. Results Protein sequencing established that albumin Zagreb is a proalbumin variant (−1Arg→Gln), and that albumin Krapina is due to a mutation within the mature polypeptide chain (573Lys→Glu). The gas chromatographic results showed that the fatty acid-binding properties of the proalbumin variant are normal, while the amino acid substitution in position 573 resulted in a general decrease of fatty acid binding. Conclusions The structural defects of the first alloalbumins, detected by routine clinical electrophoresis among the Croatian population, were characterized. Albumin Zagreb is caused by a hot-spot mutation occurring in a CpG sequence in the albumin gene. It is commonly assumed that bisalbuminaemia has no direct clinical relevance. However, the present study suggests that naturally occurring mutations can affect the ligand-binding properties of human serum albumin.

Uvod: Urođena bisalbuminemija je rijetka bolest, najčešće prisutna u benignom obliku, dosad opisivana u nekoliko patoloških stanja. Već su opisane dvije genske varijante kod dvije hrvatske obitelji. U ovom radu izvještavamo o novom slučaju bisalbuminemije kod bolesnika iz Hrvatske sa sarkoidozom. Metode: Bolesnik je, od strane liječnika opće prakse, upućen u KB „Sestre milosrdnice" na dijagnostički pregled pod sumnjom nasarkoidozu. Napravljena je kapilarna elektroforeza proteina u serumu s automatiziranim uređajem za kapilarnu elektroforezu. Rezultati: Temeljem laboratorijskih i patoloških nalaza potvrđena je sarkoidoza. Elektroforezom u serumu otkrivene su dvije različ ite frakcije albumina. Dodatna frakcija albumina bila je sporo migrirajuća. Ta sporo migrirajuća frakcija činila je 0,48, a normalna 0,51 ukupnog albumina. Sestra bolesnika također je imala bisalbuminemiju. Zaključak: Ovo je novi slučaj urođene bisalbuminemije kod bolesnika sa sarkoidozom. Ima li bisalbuminemija ikakve veze sa sarkoidozom, potrebno je tek razjasniti. Svaki slučaj pojave urođenih ili stečenih frakcija albumina trebao bi probuditi pažnju medicinskih biokemičara i kliničara, jer bi mogao pružiti uvid u evoluciju proteina kao i u fizičke, kemijske i molekularne karakteristike albumina., Background: Inherited bisalbuminemia is rare, mostly benign state, which has so far been described in several pathological conditions. Two genetic variants have already been described in two Croatian families. Herein we report a new case of bisalbuminemia in a Croatian male patient with sarcoidosis. Methods: The patient was referred by a general practitioner to our hospital for a diagnostic work up for suspected sarcoidosis. Serum capillary protein electrophoresis was performed with automated capillary electrophoresis system. Results: Based on laboratory and pathologic findings, diagnosis of sarcoidosis was confirmed. Serum electrophoresis revealed two distinct albumin bands. Additional albumin variant was slow-migrating. The slow and a normal band made up for 0.48 and 0.51 of the total albumin, respectively. The patient's sister was also bisalbuminemic. Conclusions: This is a new case of inherited bisalbuminemia in a patient with sarcoidosis. Whether bisalbuminemia has any relevance to sarcoidosis, remains to be elucidated. Clinical chemists and clinicians should be alerted by every case of either inherited or acquired albumin variant, because it could provide insight into the protein evolution as well as the physical, chemical and molecular characteristics of albumin.