Critical Sites of Serine Acetyltransferase in Lathyrus sativus L. Affecting Its Enzymatic Activities

Abstract

LsSAT2 (serine acetyltransferase in Lathyrus sativus) is the rate-limiting enzyme in biosynthesis of β-N-oxalyl-l-α,β-diaminopropionic acid (β-ODAP), a neuroactive metabolite distributed widely in several plant species including Panax notoginseng, Panax ginseng, and L. sativus. The enzymatic activity of LsSAT2 is post-translationally regulated by its involvement in the cysteine regulatory complex in mitochondria via interaction with β-CAS (β-cyanoalanine synthase). In this study, the binding sites of LsSAT2 with the substrate Ser were first determined as Glu290, Arg316, and His317 and the catalytic sites were determined as Asp267, Asp281, and His282 via site-directed/truncated mutagenesis, in vitro enzymatic activity assay, and functional complementation of the SAT-deficient Escherichia coli strain JM39. Furthermore, the C-terminal 10-residue peptide of LsSAT2 is confirmed to be critical to interact with LsCAS, and Ile336 in C10 peptide is the critical amino acid. These results will enhance our understanding of the regulation of LsSAT2 activities and the biosynthesis of β-ODAP in L. sativus.

Gene identification, expression analysis, and molecular docking of SAT and OASTL in the metabolic pathway of selenium in Cardamine hupingshanensis

“…Previous research has shown that the highly conserved β1c–β2c loop, which we defined as the β7–β8 loop, plays a key role in the binding of SAT proteins to serine (Yi et al 2013 ). In addition, the ten residues of the C-terminus of SAT are used to combine the active site of OASTL and form the cysteine synthase complex (Bogdanova and Hell 1997 ; Jez and Dey 2013 ; Ma et al 2023 ).

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