Journal of Biochemistry Advance Access originally published online on August 22, 2006
Journal of Biochemistry 2006 140(4):475-481; doi:10.1093/jb/mvj180
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© 2006 The Japanese Biochemical Society.
ARTICLE |
A Novel Enzyme, 
-Carrageenase, Isolated from a Deep-Sea Bacterium
Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima, Yokosuka 237-0061
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A 
-carrageenan–degrading Pseudoalteromonas bacterium, strain CL19, was isolated from a deep-sea sediment sample. A -carrageenase from the isolate was purified to homogeneity from cultures containing -carrageenan as a carbon source. This is the first report of the isolation of -carrageenase together with the gene sequence for the enzyme. The molecular mass of the purified enzyme was approximately 100 kDa on both SDS-PAGE and gel-filtration chromatography, suggesting that the enzyme is a monomer. The optimal pH and temperature for activity were about 7 and 35°C, respectively. The enzyme had specific activity of 253 U/mg protein. The enzyme required monovalent salts for the activity. Carbohydrates, such as sorbitol, sucrose, trehalose, improved the enzyme stability. The pattern of -carrageenan hydrolysis showed that the enzyme is an endo-type -carrageenase, and the final main product was a tetrasaccharide of the -carrageenan ideal structure with galactose 2,6-disulfate at the reducing end, indicating the enzyme cleaves the ß-1,4 linkages of its backbone structure. Furthermore, the gene (cglA) encoding the enzyme was sequenced. It encoded a mature protein of 103 kDa (917 amino acids). Remarkably, the deduced amino acid sequence showed no similarity to any reported proteins.