Cystathionine beta-synthase-like protein; (CBSL)

Function

• hydro-lyase
• catalyzes 1st step of the transsulfuration pathway
  • hydroxyl group of L-serine is displaced by L-homocysteine in a beta-replacement reaction to form L-cystathionine, precursor of L-cysteine
  • allows elimination of L-methionine & the toxic metabolite L-homocysteine
• also involved in the production of hydrogen sulfide, a gasotransmitter with signaling & cytoprotective effects on neurons
• allosterically activated by S-adenosyl-methionine/AdoMet
• activated by S-adenosylhomocysteine/AdoHcy
• binds non-covalently to a heme group that may control the redox sensitivity of the enzyme
• amino-acid biosynthesis; L-cysteine biosynthesis;
  • L-cysteine from L-homocysteine & L-serine: step 1/2

Cofactor:

• pyridoxal 5'-phosphate;

L-serine + L-homocysteine = L-cystathionine + H2O

Structure

• homotetramer
• belongs to the cysteine synthase/cystathionine beta-synthase family
• contains 1 CBS domain

Compartment

• cytoplasm
• nucleus

Notes

• duplication of the CBS gene on chromosome 21
• CBS, which was originally identified as the gene encoding cystathionine beta-synthase, & CBSL encode identical proteins

More general terms

• hydro-lyase, hydratase or dehydratase

Additional terms

• cystathionine beta-synthase (serine sulfhydrase, beta-thionase, CBS)

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=102724
• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=875