. 2017 Nov 15;243(2):107–117. doi: 10.1177/1535370217740860

Table 1.

Mammalian MAT genes and isoenzymes.

MAT gene	Protein product	MAT isoenzyme	Regulatory subunit	K_m for methionine	K_i for SAMe
MAT1A	α1	MATI (tetramer) MATIII (dimer)	None	MATI: 23 µM–1 mM MATIII: 210 µM–7 mM	MATI: 400 µM MATIII: none
MAT2A	α2	Catalytic subunit of MATII	Yes, both V1 and V2 regulate MATII by lowering the K_m for methionine, V1 also lowers the K_i for SAMe (V2 has not been examined)	4–10 µM	60 µM
MAT2B	V1 (same as β), V2	Regulatory subunit of MATII

MAT gene

Protein product

MAT isoenzyme

Regulatory subunit

K_m for methionine

K_i for SAMe

MAT1A

α1

MATI (tetramer)

MATIII (dimer)

None

MATI: 23 µM–1 mM

MATIII: 210 µM–7 mM

MATI: 400 µM

MATIII: none

MAT2A

α2

Catalytic subunit of MATII

Yes, both V1 and V2 regulate MATII by lowering the K_m for methionine, V1 also lowers the K_i for SAMe (V2 has not been examined)

4–10 µM

60 µM

MAT2B

V1 (same as β), V2

Regulatory subunit of MATII

MAT: methionine adenosyltransferase.