Two cryptosporidia species encode active creatine kinases that are not seen in other apicomplexa species.

A gene encoding creatine kinase was identified in two cryptosporidia species, Cryptosporidium muris and C. andersonii. They were syntenic and shared 91% identity 94% identity at the amino acid level and nucleotide levels respectively. The C. muris creatine kinase was characterized biochemically and shown to phosphorylate both creatine and glycocyamine with a 20-fold greater preference for creatine. The observed catalytic turnover with creatine was kcat = 30 s-1 with a catalytic efficiency of 15.4 mM-1 s-1. These values were within the range observed for other creatine kinases. A search of all the apicomplexa genomes available on EuPathDB did not reveal any other phosphagen kinase genes raising the possibility of horizontal gene transfer. However, no definitive conclusion could be drawn regarding this hypothesis given the massive amount of gene loss in the apicomplexa species which are primarily parasitic species. The implications of a creatine kinase in the parasites' infection cycle are discussed.

Characterization of a putative oomycete taurocyamine kinase: Implications for the evolution of the phosphagen kinase family.

Phosphagen kinases (PKs) are known to be distributed throughout the animal kingdom, but have recently been discovered in some protozoan and bacterial species. Within animal species, these enzymes play a critical role in energy homeostasis by catalyzing the reversible transfer of a high-energy phosphoryl group from Mg⋅ATP to an acceptor molecule containing a guanidinium group. In this work, a putative PK gene was identified in the oomycete Phytophthora sojae that was predicted, based on sequence homology, to encode a multimeric hypotaurocyamine kinase. The recombinant P. sojae enzyme was purified and shown to catalyze taurocyamine phosphorylation efficiently (kcat/KM (taurocyamine) = 2 × 10(5) M(-1) s(-1)) and glycocyamine phosphorylation only weakly (kcat/KM (glycocyamine) = 2 × 10(2) M(-1) s(-1)), but lacked any observable kinase activity with the more ubiquitous guanidinium substrates, creatine or arginine. Additionally, the enzyme was observed to be dimeric but lacked cooperativity between the subunits in forming a transition state analog complex. These results suggest that protozoan PKs may exhibit more diversity in substrate specificity than was previously thought.

Identification and characterization of a putative arginine kinase homolog from Myxococcus xanthus required for fruiting body formation and cell differentiation.

Arginine kinases catalyze the reversible transfer of a high-energy phosphoryl group from ATP to l-arginine to form phosphoarginine, which is used as an energy buffer in insects, crustaceans, and some unicellular organisms. It plays an analogous role to that of phosphocreatine in vertebrates. Recently, putative arginine kinases were identified in several bacterial species, including the social Gram-negative soil bacterium Myxococcus xanthus. It is still unclear what role these proteins play in bacteria and whether they have evolved to acquire novel functions in the species in which they are found. In this study, we biochemically purified and characterized a putative M. xanthus arginine kinase, Ark, and demonstrated that it has retained the ability to catalyze the phosphorylation of arginine by using ATP. We also constructed a null mutation in the ark gene and demonstrated its role in both certain stress responses and development.