Alternate substrates and inhibitors of 1-aminocyclopropane-1-carboxylic acid synthase

Structural analogs of (-)-S-adenosyl--methionine (SAM), in which the heterocyclic base was modified, were used to initiate studies to elucidate the active site conformation of the enzyme 1-aminocyclopropane-1-carboxylic acid (ACC) synthase, which was partially purified from Lycopersicon esculentum (tomato). These potential substrate analogs were screened for activity both as substrates and/or as inhibitors of ACC synthase. In general, ACC synthase was found to have a rather rigid specificity for the structural features of the natural substrate (SAM) in that only the purine base adenosine and adenosine analogs in which the N6 nitrogen was modified were substrates.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26684/1/0000231.pd

A tandem enzymatic sp2-C-methylation process : coupling in situ S-adenosyl-L-methionine formation with methyl transfer

A one-pot, two-step biocatalytic platform for the regiospecfic C-methylation and C-ethylation of aromatic substrates is described. The tandem process utilizes SalL (Salinospora tropica) for in situ synthesis of S-adenosyl-L-methionine (SAM), followed by alkylation of aromatic substrates using the C-methyltransferase NovO (Streptomyces spheroides). Application of this methodology is demonstrated by the regiospecific labelling of aromatic substrates via the transfer of methyl, ethyl and isotopically-labelled 13CH3, 13CD3 and CD3 groups from their corresponding SAM analogues formed in situ

Stereochemical course of the biosynthesis of 1-aminocyclopropane-1-carboxylic acid. I. Role of the asymmetric sulfonium pole and the [alpha]-amino acid center

The substrate stereospecificity of 1-aminocyclopropane-1-carboxylic acid synthase, a pyridoxal phosphate-containing enzyme, from the pericarp tissue of (tomatoes) was studied using the various stereoisomers of -adenosylmethionine (AdoMet) at both the sulfonium pole and the amino acid center. The data indicate that only the naturally occurring isomer (-)Ado-L-Met acts as substrate (Km = 20+/-5 [mu]M). Both (+/-)Ado-D-Met and (+)Ado-L-Met were inactive as substrates. The (+)Ado-L-Met (Ki = 15+/-5 [mu]M) was found to be a potent inhibitor of ACC synthase whereas (+/-)Ado-D-Met (Ki = 70+/-20 [mu]M) was less active as an inhibitor. This active isomer has the () configuration at both the sulfur and the [alpha]-carbon of the amino acid portion of AdoMet.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24811/1/0000237.pd