Apolipoprotein H (APOH), also known as Beta-2-glycoprotein 1, is a glycoprotein synthesized by liver cells and it is present in the blood associated with plasma lipoproteins. Its carbohydrate content is approximately 19% of the molecular weight and it is present in the blood associated with plasma lipoproteins. Mature mouse ApoH shares 76% and 42% aa sequence identity with human and rat ApoH, respectively. The activity of APOH appears to involve the binding of agglutenating, inhibits agglutination, and negatively charged compounds by the contact activation of the intrinsic blood coagulation pathway. APOH is found be involved in the activation of lipoprotein lipase in lipid metabolism on several classes of lipoproteins.

Apolipoprotein (apo)H (also known as beta 2 glycoprotein-I) is a glycoprotein synthesized by liver cells and it is present in the blood associated with plasma lipoproteins. APOH displays a genetically determined structural polymorphism: three alleles (APOH*1, APOH*2, APOH*3) at a single locus on chromosome 17 code for different isoforms, and population studies have shown that APOH*2 is the most frequent allele.