Genetic studies of the human plasma orosomucoid (alpha-1 acid glycoprotein)

Orosomucoid (ORM) or alpha-1 acid glycoprotein is an acute phase protein of human plasma whose function is suggested to be the competitive inhibition of cellular recognition by infective agents. Isoelectric focusing (IEF) and immunoblotting have been combined and optimum conditions have been determined for reliable classification of different ORM phenotypes. Addition of 6 M urea in an IEF gel revealed additional microheterogeneity in the ORM system which has not been previously reported. 1,667 individuals from different native ethnic groups of North and South America, Africa and New Guinea have been screened to determine the distribution of ORM alleles. Two common alleles, ORM1*1 and ORM1*2 have been observed and their frequencies were determined. Genetically independent variation consistent with expression of the ORM2 locus was observed in American and African blacks but was not observed in other sampled populations. The population allele frequencies for this new locus were 0.958, 0.025, 0.006, 0.011, for alleles ORM2*1, ORM2*2, ORM2*3, ORM2*4, respectively. Family studies confirm the autosomal codominant inheritance of the phenotypes observed at both ORM loci. ^