Characterization of a New Pantothenate Kinase Isoform from Helicobacter pylori

Abstract

Pantothenate kinase (PanK) catalyzes the first step in the biosynthesis of the essential and ubiquitous cofactor coenzyme A (CoA) in all organisms. Two well characterized isoforms of the enzyme are known: a prokaryotic PanK that predominates in eubacteria and a eukaryotic isoform that has primarily been characterized from mammalian and plant sources. Curiously, the genomes of certain pathogenic bacteria, including Helicobacter pylori and Pseudomonas aeruginosa, do not contain a PanK similar to either isoform, although these organisms possess all the other biosynthetic machinery required for CoA production. In this study we cloned, overexpressed and characterized an enzyme from Bacillus subtilis and its homologue from H. pylori and show that they catalyze the ATP-dependent phosphorylation of pantothenate. These enzymes do not share sequence homology with any known PanK, and unlike the bacterial and eukaryotic PanK isoforms their activity is not regulated by either CoA or acetyl-CoA. They also do not accept the pantothenic acid antimetabolite N-pentylpantothenamide as a substrate or are inhibited by it. Taken together, these results point to the identification of a third distinct isoform of PanK that accounts for the only known activity of the enzyme in pathogens such as H. pylori and P. aeruginosa.

Structure of the Type III Pantothenate Kinase from Bacillus anthracis at 2.0 Å Resolution: Implications for Coenzyme A-Dependent Redox Biology,

“…The type III BsPanK also exhibited a five-to-six-fold increase in K m (Pan) relative to EcPanK and SaPanK; this correlates with the observation that N5-Pan is neither an alternate substrate for nor a competitive inhibitor of BsPanK. Limited bioinformatics analyses suggested that both type II and type III PanKs belonged to the ribonuclease H-like family [kinase family and fold group 4 (15)] of kinases (18). Very recently, Hong et al (19) and Yang et al (20) have confirmed these predictions with crystal structures for the type II SaPanK-AMPPNP complex and for the type III PanKs from Pseudomonas aeruginosa (PaPanK) and Thermotoga maritima (TmPanK), as well as the PaPanK-Pan complex.…”

“…In 2005, the bacterial type II and type III PanKs were identified in S. aureus (17), and in Helicobacter pylori and Bacillus subtilis (18), respectively. Neither isoform is similar in sequence to the type I EcPanK, nor is either subject to feedback inhibition by CoASH.…”

Superessential reactions in metabolic networks

“…These genes do not share sequence similarity (39), but they, nonetheless, encode enzymes that catalyze the same reaction. The enzyme encoded by coaA is of type I, whereas the enzyme encoded by coaX is a type III enzyme (39,40). The existence of the alternative coaX explains the low genome occurrence of coaA, but it also reinforces the essentiality of the reaction.…”

Feedback Inhibition of Pantothenate Kinase Regulates Pantothenol Uptake by the Malaria Parasite

“…Experiments using lysate provide a useful tool for studying phosphorylation independently of transport but do not take into account the regulation of phosphorylation in situ. CoA and/or its esters have been shown to inhibit the PanKs of bacteria, plants, and animals (1), although recently the PanKs from Staphylococcus aureus and Helicobacter pylori have been shown to be refractory to this feedback inhibition (29,30). We therefore investigated the effects of CoA on PfPanK activity.…”