Targeting S-adenosylmethionine biosynthesis with a novel allosteric inhibitor of Mat2A

Abstract

S-Adenosyl-L-methionine (SAM) is an enzyme cofactor used in methyl transfer reactions and polyamine biosynthesis. The biosynthesis of SAM from ATP and L-methionine is performed by the methionine adenosyltransferase enzyme family (Mat; EC 2.5.1.6). Human methionine adenosyltransferase 2A (Mat2A), the extrahepatic isoform, is often deregulated in cancer. We identified a Mat2A inhibitor, PF-9366, that binds an allosteric site on Mat2A that overlaps with the binding site for the Mat2A regulator, Mat2B. Studies exploiting PF-9366 suggested a general mode of Mat2A allosteric regulation. Allosteric binding of PF-9366 or Mat2B altered the Mat2A active site, resulting in increased substrate affinity and decreased enzyme turnover. These data support a model whereby Mat2B functions as an inhibitor of Mat2A activity when methionine or SAM levels are high, yet functions as an activator of Mat2A when methionine or SAM levels are low. The ramification of Mat2A activity modulation in cancer cells is also described.

Control and regulation of S‐Adenosylmethionine biosynthesis by the regulatory β subunit and quinolone‐based compounds

“…Triphosphate is a product intermediate generated from SAMe formation and it has to be hydrolyzed before being released from the active site to allow MAT enzyme to regenerate for the next reaction cycle. The underlying mechanism by which the observed activities of the mutants are recovered by complex formation is in part facilitated by the profound increase in phosphatase activities of the enzyme complexes and is consistent with the protein dynamics study that showed MATα2 ATP‐binding region to undergo allosteric modification upon binding of MATβ . Structural comparison of the wt MATα2 and MATα2β complex revealed that conformation of the residues in the catalytic site of wt MATα2 is unaltered upon complex formation with MATβ; however, several movements of the solvent exposed α‐helices are found in the complex formation.…”

“…A). The observation that the interaction with MATβV1/V2 can modulate and restore function of the pathogenic mutant enzyme activity offers possibility of chemical intervention in finding therapeutic solutions using recently discovered the effect of compounds with triazoloquinoline cores on wt MATα2 .…”

“…The binding of MATβ to MATα2 may propagate from the MATβ‐binding site (Gln190‐Ile198) to regions connecting the active and allosteric site (Ile241‐Tyr271, Gly272‐Thr288), and the region (Ala109‐Gly140) that contains gating loop domain of MATα2 (Gln113‐Gly131). The substrate binding and product release are likely linked to and modulated by MATβ binding to the MATα2 allosteric site offering the use of heterodimeric interface as a target for chemical intervention: either stabilization of defective enzymes or inhibition of the overexpressed enzymes .…”

Phenylethynyl-substituted heterocycles inhibit cyclin D1 and induce the expression of cyclin-dependent kinase inhibitor p21Wif1/Cip1in colorectal cancer cells

“…As desired, these stilbene-based agents did not affect methionine S-adenosyltransferase-1 (MAT1) 16–19 that served as the principal source of SAM necessary for other cellular needs. Unlike a recent report 20 of other MAT2A inhibitors, we also demonstrated in vivo potency in a xenograft model using colorectal cancer cells 12 .…”

SAMTOR is an S -adenosylmethionine sensor for the mTORC1 pathway

“…The enzyme methionine adenosyltransferase (MAT) synthesizes SAM from adenosine triphosphate and methionine, an essential amino acid, so that starvation for methionine should lower SAM levels, as has been observed in other systems (25, 26). Indeed, SAM concentrations in HEK-293T cells decreased upon methionine starvation, falling from above the dissociation constant of SAMTOR for SAM to below it (Fig.…”