D-arabinofuranose (Araf) exists in the D-arabinan parts of the lipoarabinomannan (LAM) and arabinogalactan (AG) in the cell wall fraction of Mycobacteria. The D-arabinan structure is commonly constituted by α-1,5-D-Araf backbone with some α-1,3-D-Araf branching, and is terminated by β-1,2-Araf structure. Endo-D-arabinase is a D-arabinan degrading enzyme with endo-mode of action. The enzyme has been found in Microbacterium arabinogalactanolyticum, Cellulomonas sp. and Mycobacterium smegmatis, whereas the gene information has never been reported. Here, we would like to report the cloning and characterization of novel endo-D-arabinases (Endo-MA1 and Endo-MA2) from Mi. arabinogalactanolyticum JCM9171. Endo-MA1 is a novel glycoside hydrolase which has no similarities with any known CAZy GH families. The enzyme comprises 511 aa including a N-terminal signal peptide, a catalytic domain and a C-terminal carbohydrate-binding domain. Endo-MA2 (27% identity with Endo-MA1) is located in same gene cluster. Endo-MA2 comprises 369 aa including a N-terminal signal peptide and a catalytic domain. The recombinant enzymes degraded LAMs from My. smegmatis and My. turberculosis, and released arabinooligosaccharides (DPs 1 - &gt;20), whereas the degradation profiles were different in each enzyme. The enzymes also degraded AG from My. smegmatis. The substrate specificities were examined by using synthetic oligo-D-arabinofuranosides.

Characterization of mycobacterial arabinan degrading enzymes from Microbacterium arabinogalactanolyticum

2019 Fall National Meeting

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