Mutational effects on carbapenem hydrolysis of YEM-1, a new sub-class B2 metallo-β-lactamase from Yersinia mollaretii

Abstract

1The analysis of the genome sequence of Yersinia mollaretii (Y. mollaretii) ATCC 43969 indicates 2 the presence of the bla YEM gene coding for YEM-1, a putative subclass B2 metallo-β-lactamase. The 3 objectives of our work were to produce, purify and complete the kinetic characterization of Compared to the known subclass B2 metallo−β-lactamases, YEM-1 displayed a narrowest substrate 5 profile since it is only able to hydrolyse imipenem with a high catalytic efficiency but not all the 6 other carbapenems tested such as biapenem, meropenem, doripenem and ertapenem. A possible 7 explanation of this peculiar activity profile is the presence of tyrosine 67 (loop L1), threonine 156 8 (loop L2) and serine 236 (loop L3) respectively. We showed that the substitution of Y67 broadened 9 the activity profile of the enzyme for all carbapenems but still displayed a poor activity toward the 10 other β-lactam classes. The genus Yersinia belonging to the family of Enterobacteriaceae shows three mains groups of 31 human pathogen strains, Yersinia pestis (Y. pestis), Yersinia pseudotuberculosis (Y. pseudo-32 tuberculosis) and Yersinia enterolitica (Y. enterocolitica). Y. pestis, the bacterial agent of bubonic 33 plague, escapes the macrophages action and is the cause of a lethal bacteremia without antibiotic 34 treatments (1). A new threat is the emergence of a multidrug resistant Y. pestis strain (2). Y. 35 pseudotubercolis and Y. enterocolitica are important cause of gastroenteritis in human following the 36 ingestion of undercooked or contaminated pork and vegetables (3-4). Others Yersinia species like Y. 37 fredricksenii, Y. kristensenii, Y. intermedia, Y. mollaretii, Y. bercovieri and Y. rohdei are considered 38 as not pathogen for human (5-6). Our interest was focused on Y. mollaretii. This specie, previously 39 known as Y. enterocolitica-like organism biogroup A, was renamed Yersinia mollaretii and 40 assigned in the new biogroup 3A by Wauters et al (7). The majority of those strains were isolated 41 from environmental sources such as soil, drinking water, raw vegetables, and meat but few were 42 clinical isolates from patient stools affected by gastrointestinal disease. It was demonstrated that it 43 can colonize the low level of the human ileum but the absence of human virulence markers 44 classified this strain as non-pathogenic and saprophyte (8). The sequence genome of the reference 45 strain Y. mollaretii ATCC 43969 (numbered as CCUG26331, CDC2465-87, CIP103324 and 46 DSM18520 in other biobanks) was determined (NCBI Reference Sequence: 47 NZ_AALD02000006.1). Its analysis indicated the presence of two β-lactamase genes, namely blaB 48 coding for an AmpC-like enzyme and one coding for a putative sub-class B2 metallo β-lactamase 49 called YEM-1 (YErsinia Metallo-β-lactamase -GenBank: EEQ11779.1). It is interesting to note the 50 absence of the blaA gene encoding for an Extented Spectrum class A β-Lactamase found in other 51 Yersinia species (9-12). This observation is in good agreement with the phenotypic studies showing...