Selenocysteine residues are present in

Selenocysteine is defined as substance with Cysteine containing selenium in place of one sulfur atom.Deiodinase is an enzyme that deiodinates two of the iodinated amino acids (iodothyronines) within the thyroid gland. Selenium-dependent deiodinase conves thyroxine (T4) to triiodothyronine (T3), the more active thyroid hormone.Pyruvate carboxylase an enzyme that catalyzes the irreversible carboxylation of pyruvate, a reaction necessary for gluconeogenesis from lactate or amino acids forming pyruvate and also providing four-carbon compounds for the citric acid cycle. The enzyme is a mitochondrial protein occurring in liver but not in muscle. Deficiency of the enzyme, an autosomal-recessive trait, causes severe psychomotor retardation and lactic acidosis in infants.Xanthine oxidase flavoprotein containing molybdenum; an oxidoreductase catalyzing the reaction of xanthine, O2, and H2O to produce urate and superoxide. Also oxidizes hypoxanthine, some other purines and pterins, and aldehydes. A lower rate of oxidation is observed in patients with molybdenum cofactor deficiency.Lysyl oxidase is an enzyme, which requires Cu2+ and O2, that oxidizes ceain lysyl residues in collagen to allysyl residues andhydroxylysyl residues to hydroxyalkyl residues; this is a required step for the crosslinking ( aldol condensations and through Amadori rearrangements) of collagen strands; a lower activity of this enzyme is associated with occipital horn syndrome.