Sulfur-Element containing metabolic pathways in human health and crosstalk with the microbiome.

In humans, methionine derived from dietary proteins is necessary for cellular homeostasis and regeneration of sulfur containing pathways, which produce inorganic sulfur species (ISS) along with essential organic sulfur compounds (OSC). In recent years, inorganic sulfur species have gained attention as key players in the crosstalk of human health and the gut microbiome. Endogenously, ISS includes hydrogen sulfide (HS), sulfite (SO), thiosulfate (SO), and sulfate (SO), which are produced by enzymes in the transsulfuration and sulfur oxidation pathways.

Gamma cleavage is a rate-determining step in the gamma-elimination reaction of L-methionine analogues catalyzed by methionine-gamma-lyase.

Methionine-γ-lyase (MGL) is a pyridoxal-5'-phosphate dependent enzyme found in bacteria and protozoa that catalyzes a variety of reactions, including the γ-elimination of L-methionine (L-Met). Here we report experimental kinetic data and density functional theory (DFT) computational data for the γ-elimination reaction of L-Met and several other substrate analogues by a recombinant MGL from P. gingivalis (MGL_Pg).

A continuous spectrophotometric assay and nonlinear kinetic analysis of methionine γ-lyase catalysis.

In this article, we present a new, easy-to-implement assay for methionine γ-lyase (MGL)-catalyzed γ-elimination reactions of l-methionine and its analogues that produce α-ketobutyrate (α-KB) as product. The assay employs ultraviolet-visible (UV-Vis) spectrophotometry to continuously monitor the rate of formation of α-KB by its absorbance at 315 nm. We also employ a nonlinear data analysis method that obviates the need for an "initial slope" determination, which can introduce errors when the progress curves are nonlinear.