Ruminiclostridium josui Abf62A-Axe6A: A tri-functional xylanolytic enzyme exhibiting α-l-arabinofuranosidase, endoxylanase, and acetylxylan esterase activities.
Enzyme Microb Technol
; 117: 1-8, 2018 Oct.
Article
in En
| MEDLINE
| ID: mdl-30037546
ABSTRACT
Ruminiclostridium josui Abf62A-Axe6A is a modular enzyme comprising (in order from the N-terminus) an N-terminal signal peptide, a glycoside hydrolase family 62 (GH62) catalytic module, a family 6 carbohydrate binding module (CBM6), a dockerin module and an additional carbohydrate esterase family 6 catalytic module (CE6). In this study, three Abf62A-Axe6A derivatives were constructed, overexpressed in Escherichia coli, purified, and biochemically characterized RjAbf62A-Axe6A, containing all four modules but lacking the signal peptide; RjAbf62A-CBM6, containing the GH62 and CBM6 modules; and RjAxe6A, containing only CE6. RjAbf62A-Axe6A was highly active toward arabinoxylan and moderately active toward sugar beet arabinan, and released mainly arabinose. Analysis of the arabinoxylooligosaccharide hydrolysis products revealed that RjAbf62A-Axe6A released α-1,2- and α-1,3-linked arabinofuranose from both singly and doubly substituted xylosyl residues. Furthermore, RjAbf62A-Axe6A exhibited a weak activity toward linear 1,5-α-l arabinan and arabinooligosaccharides, indicating that it is capable of cleaving α-1,5-linkage. Surprisingly, RjAbf62A-Axe6A also demonstrated an endoxylanase activity toward birchwood and beechwood xylans and xylooligosaccharides. Although RjAbf62A-CBM6 exhibited a similar substrate specificity to RjAbf62A-Axe6A, RjAbf62A-CBM6 showed lower activities toward soluble arabinoxylans, birchwood and beechwood xylans and arabinoxylooligosaccharides but not toward insoluble arabinoxylan. RjAbf62A-Axe6A is the first reported GH62 enzyme with α-l-arabinofuranosidase and endoxylanase activities. Although both RjAbf62A-Axe6A and RjAxe6A had acetylxylan esterase activities, RjAbf62A-Axe6 exhibited a higher activity toward insoluble wheat arabinoxylan compared with RjAxe6.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Acetylesterase
/
Xylans
/
Endo-1,4-beta Xylanases
/
Clostridiales
/
Glycoside Hydrolases
Language:
En
Journal:
Enzyme Microb Technol
Year:
2018
Document type:
Article