European Journal of Pediatrics

, Volume 157, Supplement 2, pp S40–S44 | Cite as

The metabolism of homocysteine: pathways and regulation

  • J. D. Finkelstein


Two pathways, the methionine cycle and transsulfuration, account for virtually all methionine metabolism in mammals. Every tissue possesses the methionine cycle. Therefore, each can synthesize AdoMet, employ it for transmethylation, hydrolyze AdoHcy, and remethylate homocysteine. Transsulfuration, which occurs only in liver, kidney, small intestine and pancreas, is the means for catabolizing homocysteine. Liver has a unique isoenzyme of MAT that allows the utilization of excess methionine for the continued synthesis of AdoMet. Metabolic regulation is based on the distribution of available homocysteine between remethylation and conversion to cystathionine. The tissue content of the enzymes and their inherent kinetic properties provide the basis for the regulatory mechanism. The effector properties of the metabolites AdoMet, AdoHcy and methylTHF are of particular relevance.

Key words Methionine Homocysteine Transsulfuration Transmethylation S-adenosylmethionine 

Copyright information

© Springer-Verlag Berlin Heidelberg 1998

Authors and Affiliations

  • J. D. Finkelstein
    • 1
  1. 1.Medical Service, Veterans Affairs Medical Center, 50 Irving Street, N.W., Washington, DC 20 422, USA, Tel.: 202 745-8121, Fax: 202 745 8184US

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