[Mechanisms that protect against homocysteine toxicity].
Elevated concentrations of homocysteine (Hcy) in human tissues have been correlated with some diseases, such as cardio-vascular, neurodegenerative, and kidney disorders. Hcy occurs in human blood in several forms. The most reactive is homocysteine thiolactone (HcyTl). It spontaneously homocysteinylates proteins impairing their functions. As has been evidenced recently, organisms developed protective mechanisms against the HcyTl toxicity. The first mechanism discovered was the calcium-dependent enzyme occurring in mammalian sera, known till then as paraoxonase, which hydrolyzes HcyTl to Hcy. Chronologically second mechanism discovered was urinary excretion of HcyTl. The third protective mechanism is the HcyTl hydrolysis catalyzed by intracellular enzyme known as bleomycin hydrolase. This review outlines current knowledge of the Hcy toxicity and of the three aforementioned protective mechanisms, emphasizing the role of bleomycin hydrolase/ homocysteine-thiolactonase.
Zimny
Jarosław
J
Katedra Biochemii i Biotechnologii, Akademia Rolnicza im. A. Cieszkowskiego w Poznaniu. zimny@au.poznan.pl
D043303:Aryldialkylphosphatase / Q000378:metabolism*; D002318:Cardiovascular Diseases / Q000378:metabolism; D003546:Cysteine Endopeptidases; D006710:Homocysteine / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity*; D006801:Humans; D006867:Hydrolases / Q000378:metabolism*; D006868:Hydrolysis
D006710:Homocysteine; C007957:homocysteine thiolactone; D006867:Hydrolases; D043303:Aryldialkylphosphatase; D003546:Cysteine Endopeptidases; C031262:bleomycin hydrolase