A cDNA encoding a β-1,4-d-mannanase (CaMan) was identified among the expressed sequence tags (ESTs) of the Antarctic springtail, Cryptopygus antarcticus. The open reading frame consisted of 1149 bp encoding 382 amino acids with a putative signal peptide. Amino acid sequence comparison with other mannanases indicated that CaMan likely belongs to subfamily 10 of the glycoside hydrolase family 5, together with mollusc β-mannanases. CaMan shows typical features of a cold-active enzyme: it has a high frequency of polar residues such as Asn, Gln, and Ser, and a low frequency of hydrophobic residues as well as a low ratio of Arg/(Arg + Lys) compared to the mesophilic β-mannanases. When CaMan was fused with the thioredoxin gene in pET-32a(+), expressed in E. coli Rosetta-gami (DE3), and purified after thrombin treatment, catalytically active enzyme was obtained. CaMan has high specific activity (416.3 U/mg) toward locust bean gum at an optimal temperature of 30 °C and an optimal pH of 3.5. Its optimal temperature is the lowest among those of the known mannanases and the optimal pH is also the lowest except those of fungi. Even at 0-5 °C, this enzyme retained 20-40% of its maximum activity. Divalent metal ions such as Ca2+, Mg2+, Cu2+, and Zn2+ enhanced the enzyme activity, but Mn2+, Hg2+, and Ag+ inhibited activity. This study represents the first record of a β-mannanase from an arthropod and provides a new source of carbohydrate hydrolysis enzyme with novel characteristics.
|Original language||English (US)|
|Number of pages||9|
|Journal||Comparative Biochemistry and Physiology - B Biochemistry and Molecular Biology|
|State||Published - Sep 2008|
Bibliographical noteFunding Information:
This research was supported by the Marine and Extreme Genome Research Center program of the Ministry of Maritime Affairs and Fisheries, Republic of Korea.
Copyright 2020 Elsevier B.V., All rights reserved.
- Antarctic springtail
- Cold activity
- Cryptopygus antarcticus
- GH5 family
- Low pH activity