The unexpected M60-like/PF13402-CBM combinations we observed led us to ask how commonly CBMs are linked to peptidases by searching the MEROPS database for annotated peptidases possessing CBM5_12, CBM32 or CBM51. Using HMMER searches with a conservative cut off value we identified 141 MEROPS entries positive for CBM32 and/or CBM5_12. None were positive for CBM51. A total of 110 proteins from 16 peptidase families were positive for the CBM32 domain, whereas 31 proteins from nine peptidase families were positive for the CBM5_12 domain, indicating that these CBMs are widely distributed across annotated peptidases. One MEROPS entry from Vibrio campbellii was positive for both CBM32 and CBM5_12 and is a member of the Zn-metallopeptidase family M64. In contrast to the M60-like/PF13402 containing proteins the SCH772984 domain composition of M60-enhancin/PF03272 containing proteins was much less diverse and shared with the former CBM5_12 and fibronectin type III domains. Most of the 415 M60-like/PF13402-containing proteins were predicted to MK-2206 2HCl supply possess a signal peptide, one or more transmembrane domains or a bacterial lipoprotein motif. These features suggest M60-like/ PF13402-containing proteins are extracytoplasmic, either secreted or anchored at the surface of microbial cells and could therefore act on extracellular targets. In contrast, no extracellular- associated sequence features were detected in the 14 M60like/PF13402-containing proteins from animals or the M60- like/PF13402-containing proteins from plant pathogens. Similarly, the majority of the 141 non-M60-like/PF13402 MEROPS entries positive for CBM32 and/or CBM5_12 were predicted to possess a SP and/or one or more TMD suggesting these peptidases also target extracellular glycoproteins. The predicted peptidase and glycan binding activities, cellular location and taxonomic distribution of a number of M60-like/ PF13402 containing proteins suggest their target substrates are host glycoproteins such as mucins. In addition, a previous study has shown that genes encoding two of the three M60-like/ PF13402 domain containing proteins with the gluzincin motif from the human gut bacterium Bacteroides thetaiotaomicron are upregulated in response to host O-glycan mucins, both in vitro and in vivo. To experimentally test the hypothesis that some M60-like/ PF13402 containing proteins degrade mucins we expressed and purified full-length BT4244 and constructs lacking either its Nterminal putative carbohydrate binding domains BACON and CBM32 or C-terminal M60-like/PF13402 peptidase domain and assessed their ability to degrade mucins using a gel based assay.