THE GENE ENCODING THE KAPPA-CARRAGEENASE OF ALTEROMONAS-CARRAGEENOVORA IS RELATED TO BETA-1,3-1,4-GLUCANASES

The nucleotide (nt) and deduced amino acid (aa) sequences are reported for the structural gene cgkA encoding kappa-carrageenase (M(r) 44 412)from the marine bacterium Alteromonas carrageenovora (ATCC 43555), a hydrolase involved in the degradation of kappa-carrageenan. The cgkA gene codes for a protein of 397 aa, with a signal peptide of 25 aa. The enzyme is a new member of family 16 of glycosyl hydrolases, which comprises beta-1,3-1,4-glucanases from various sources and the beta-agarase of Streptomyces coelicolor. It is proposed that residue Glu(163) in the kappa-carrageenase from A. carrageenovora and Glu(155) in the beta-agarase from S. coelicolor are important for catalysis.