Abstract
The genome of Helicobacter pylori encodes for carbonic anhydrases (CAs, EC 4.2.1.1) belonging to the α- and β-CA classes, which together with urease, have a pivotal role in the acid acclimation of the microorganism within the human stomach. Recently, in the exoproteome of H. pylori, a CA with no indication of the corresponding class was identified. Here, using the protonography and the mass spectrometry, a CA belonging to the α-class was detected in the outer membrane vesicles (OMVs) generated by planktonic and biofilm phenotypes of four H. pylori strains. The amount of this metalloenzyme was higher in the planktonic OMVs (pOMVs) than in the biofilm OMVs (bOMVs). Furthermore, the content of α-CA increases over time in the pOMVs. The identification of the α-CA in pOMVs and bOMVs might shed new light on the role of this enzyme in the colonization, survival, persistence, and pathogenesis of H. pylori.
Highlights
In prokaryotes, the existence of genes encoding carbonic anhydrases (CAs, EC 4.2.1.1) belonging to the a, b- and c-classes suggests that these enzymes play an important role in the prokaryotic physiology[1,2,3,4,5,6]
Helicobacter pylori is the causative agent of gastritis, peptic, and duodenal ulcer as well as MALT lymphoma and gastric cancer[1,14,15]
Two different CAs are encoded by the genome of H. pylori: the periplasmic a-CA and the cytoplasmic b-CA
Summary
The existence of genes encoding carbonic anhydrases (CAs, EC 4.2.1.1) belonging to the a-, b- and c-classes suggests that these enzymes play an important role in the prokaryotic physiology[1,2,3,4,5,6]. The occurrence and significance of the two CAs and their joint activities with urease have been widely studied to maintain the H. pylori periplasmic and cytoplasmic pH close to neutrality in the highly acidic gastric environment. Helicobacter pylori buffers its periplasm by means of CO2/HCO3À and NH3/NH4þ couples produced by the reactions catalyzed by urease and the a- and b-CAs17. The gene deletion or inhibition of the H. pylori CAs determined a reduced stomach and duodenum colonization in vivo limiting the bacterial survival within the highly acid environment[18,19]. Current studies report that the EPS matrix of H. pylori biofilm is constituted by proteomannans, LPS-related structures, extracellular DNA (eDNA), proteins, and outer membrane vesicles (OMVs)[30,31].
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