A novel enzyme, lambda-carrageenase, isolated from a deep-sea bacterium.
A lambda-carrageenan-degrading Pseudoalteromonas bacterium, strain CL19, was isolated from a deep-sea sediment sample. A lambda-carrageenase from the isolate was purified to homogeneity from cultures containing lambda-carrageenan as a carbon source. This is the first report of the isolation of lambda-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 degrees 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 lambda-carrageenan hydrolysis showed that the enzyme is an endo-type lambda-carrageenase, and the final main product was a tetrasaccharide of the lambda-carrageenan ideal structure with galactose 2,6-disulfate at the reducing end, indicating the enzyme cleaves the beta-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.
Ohta
Yukari
Y
Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima, Yokosuka. ohtay@jamstec.go.jp
Hatada
Yuji
Y
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001483:Base Sequence; D002241:Carbohydrates / Q000737:chemistry; D002351:Carrageenan / Q000378:metabolism*; D004795:Enzyme Stability; D019015:Geologic Sediments / Q000382:microbiology; D006026:Glycoside Hydrolases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008969:Molecular Sequence Data; D031161:Pseudoalteromonas / Q000201:enzymology*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity; D013696:Temperature
D001426:Bacterial Proteins; D002241:Carbohydrates; D011994:Recombinant Proteins; D002351:Carrageenan; D006026:Glycoside Hydrolases; C516835:lambda-carrageenase, Pseudoalteromonas