| Clinical conditions associated with abnormal plasma concentrations of specific liver proteins
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| Genetic deficiency of α1-antitrypsin presents in infancy as liver disease, or in adulthood as lung disease
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| Hepatic α1 antitrypsin, belongs to serpins, one of the family of serine protease inhibitors, and has, contrary to its name, macrophage-derived elastase as its predominant target protease. Genetic deficiency of α1-antitrypsin presents in infancy as liver disease, or in adulthood as lung disease caused by elastase-mediated tissue destruction; the severity of the liver disease associated with α1-antitrypsin deficiency is variable. Several isoforms of α1-antitrypsin exist as a result of allelic variation: the normal isoform is known as M, and the two common defective isoforms as S and Z; the null allele produces no α1-antitrypsin.
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| Genetic deficiency of ceruloplasmin itself leads to Wilson's disease, a condition associated with damage to both the liver and the CNS
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| Ceruloplasmin is the major copper-containing protein of the liver and plasma, and functions as an iron oxidizing (ferroxidase) enzyme: oxidation of Fe2+ to Fe3+ is necessary for the mobilization of stored iron, and nutritional copper deficiency produces anemia. Genetic deficiency of ceruloplasmin itself leads to Wilson's disease, a condition associated with damage to both the liver and the CNS. The liver also synthesizes proteins responsible for storage (ferritin) and transport (transferrin) of iron (see Chapter 3).
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| Particularly high plasma concentrations of α-fetoprotein are associated with liver cancer
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| α-fetoprotein (AFP) and albumin have considerable sequence homology, and appear to have evolved by reduplication of a single ancestral gene. In the fetus, AFP appears to serve physiologic functions similar to those performed by albumin in the adult; furthermore, by the end of the first year of life, AFP in the plasma is entirely replaced by albumin. During hepatic regeneration and proliferation, AFP is again synthesized: particularly high plasma concentrations of AFP are associated with liver cancer.
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