The Arginine Kinase from the Tick Rhipicephalus sanguineus Is an Efficient Biocatalyst

Abstract

Arginine kinase (AK) is a reversible enzyme that regulates invertebrates’ phosphagenarginine phosphate levels. AK also elicits an immune response in humans, and it is a major foodallergen in crustacea and may be a target for novel antiparasitic drugs. Although AK has beenprimarily described in the shrimp, it is also present in other invertebrates, such as the brown tickRhipicephalus sanguineus (Rs), the vector for Rocky Mountain Spotted Fever. Here we report theenzymatic activity and the crystal structure of AK from Rhipicephalus sanguineus (RsAK) in an openconformation without substrate or ligands and a theoretical structure of RsAK modeled bound withthe substrate/product (Arg-ADP) in a closed conformation. The Michaelis-Menten kinetics confirmedthat RsAK is an efficient biocatalyst due to its high kcat/Km parameter. The recombinant enzymewas expressed in bacteria and purified to a 20 mg/L culture yield. AK is an essential enzyme ininvertebrates. Future work will be focused on the RsAK enzymatic inhibition that may lead to novelstrategies to control this pest, a burden to animal and human health.