Protein
Cystathionine gamma-synthase 1, chloroplastic
Organism
Arabidopsis thaliana
Function
Catalyzes the first committed step of methionine (Met) biosynthesis. Catalyzes the formation of L-cystathionine from homoserine esters and L-cysteine, via a gamma-replacement reaction. Substrate preference for cystathionine synthesis is O-phospho-L-homoserine (OPH) > O(4)-succinyl-L-homoserine (OSH) >> O-acetyl-L-homoserine (OAH). Is able, at extremely low rate, to catalyze a gamma-elimination of OPH in the absence of cysteine to produce inorganic phosphate (Pi), 2-oxobutanoate and ammonia.
Similarity
Belongs to the trans-sulfuration enzymes family.
Sequence
MAVSSFQCPTIFSSSSISGFQCRSDPDLVGSPVGGSSRRRVHASAGISSSFTGDAGLSSRILRFPPNFVRQLSIKARRNCSNIGVAQIVAAKWSNNPSSALPSAAAAAATSSASAVSSAASAAAASSAAAAPVAAAPPVVLKSVDEEVVVAEEGIREKIGSVQLTDSKHSFLSSDGSLTVHAGERLGRGIVTDAITTPVVNTSAYFFKKTAELIDFKEKRSVSFEYGRYGNPTTVVLEDKISALEGAESTLVMASGMCASTVMLLALVPAGGHIVTTTDCYRKTRIFMENFLPKLGITVTVIDPADIAGLEAAVNEFKVSLFFTESPTNPFLRCVDIELVSKICHKRGTLVCIDGTFATPLNQKALALGADLVVHSATKYIGGHNDVLAGCICGSLKLVSEIRNLHHVLGGTLNPNAAYLIIRGMKTLHLRVQQQNSTAFRMAEILEAHPKVSHVYYPGLPSHPEHELAKRQMTGFGGVVSFEIDGDIETTIKFVDSLKIPYIAPSFGGCESIVDQPAIMSYWDLPQEERLKYGIKDNLVRFSFGVEDFEDVKADILQALEAI