The members of the Complex Iron-Sulfur Molydoenzyme (CISM) family catalyzes a variety of substrate transformations important in microbial life processes. Structurally, this group of enzymes is also very diverse with different amino acid coordinating to the Mo-active center. Molybdenum coordination has long been proposed to impact the catalytic activity of the enzyme, however, exactly how they tune the substrate preference is not clear. Here we provide a kinetic underpinning of the differences imposed by exchanging the molybdenum ligands. To this end, catalytic subunit of periplasmic nitrate reductase (NapA) from <i>Campylobacter jejuni</i> as a model. NapA has been heterologously overexpressed, and a series of variants, where the molybdenum coordinating cysteine has been replaced with another amino acid, has been produced. The kinetic properties of these variants are discussed and compared with those of the native enzyme, providing quantitative information to understand the function of the molybdenum coordinating residue.

Defining the catalytic preference in complex iron-sulfur molydoenzyme (CISM) family

ACS Fall 2021

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