The domain within your query sequence starts at position 4 and ends at position 326; the E-value for the SAM_decarbox domain shown below is 1.5e-126.

AHFFEGTEKLLEVWFSRQQSDASQGSGDLRTIPRSEWDVLLKDVQCSIISVTKTDKQEAY
VLSESSMFVSKRRFILKTCGTTLLLKALVPLLKLARDYSGFDSIQSFFYSRKNFMKPSHQ
GYPHRNFQEEIEFLNAIFPNGAAYCMGRMNSDCWYLYTLDFPESRVISQPDQTLEILMSE
LDPAVMDQFYMKDGVTAKDVTRESGIRDLIPGSVIDATLFNPCGYSMNGMKSDGTYWTIH
ITPEPEFSYVSFETNLSQTSYDDLIRKVVEVFKPGKFVTTLFVNQSSKCRTVLSSPQKID
GFKRLDCQSAMFNDYNFVFTSFA

SAM_decarbox

SAM_decarbox
PFAM accession number:PF01536
Interpro abstract (IPR001985):

S-adenosylmethionine decarboxylase (AdoMetDC) [ (PUBMED:10378277) ] catalyzes the removal of the carboxylate group of S-adenosylmethionine to form S-adenosyl-5'-3-methylpropylamine which then acts as the n-propylamine group donor in the synthesis of the polyamines spermidine and spermine from putrescine.

The catalytic mechanism of AdoMetDC involves a covalently-bound pyruvoyl group. This group is post-translationally generated by a self-catalyzed intramolecular proteolytic cleavage reaction between a glutamate and a serine. This cleavage generates two chains, beta (N-terminal) and alpha (C-terminal). The N-terminal serine residue of the alpha chain is then converted by nonhydrolytic serinolysis into a pyruvyol group.

GO process:spermidine biosynthetic process (GO:0008295), spermine biosynthetic process (GO:0006597)
GO function:adenosylmethionine decarboxylase activity (GO:0004014)

This is a PFAM domain. For full annotation and more information, please see the PFAM entry SAM_decarbox