Carbohydrate Binding Module Family 92

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• Author: Xuanwei Mei

• Responsible Curator: Yaoguang Chang

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CAZy DB link

https://www.cazy.org/CBM92.html

Ligand specificities

The first characterized member in the CBM92 family is the Cgk16A-CBM92 from a marine bacterium Wenyingzhuangia aestuarii OF219 [1]. The CBM92 bound specifically to carrageenan. It was incapable of binding to other polysaccharide components in red algae including agarose, porphyran, and funoran [1]. Meanwhile, the CBM92 displayed no affinity to several anionic polysaccharides, namely pectin, chondroitin sulfates, dermatan sulfate, and sulfated fucans [1]. The Cgk16A-CBM92 showed no significant difference in the affinity to κ- and ι-carrageenan.

Structural Features

No three-dimensional structure has been solved in this CBM family at present. Several conserved residues (e.g., Phe-70, Arg-72, and Phe-75) were discovered through the multiple sequence alignments of Cgk16A-CBM92 and its close homologs [1], which might be critical for the ligand binding of this CBM.

Functionalities

Figure 1. Domain architecture of the κ-carrageenase Cgk16A. The enzyme consists of a signal peptide (1-20 amino acids), a GH16 domain (21-347 amino acids), a CBM92 domain (viz., Cgk16A-CBM92; 378-490 amino acids) and a C-terminal Sorting domain (516-581 amino acids).

In the natural context, Cgk16A-CBM92 is a component of the κ-carrageenase Cgk16A [2] (Fig. 1). It thus might maintain the enzyme near its substrate to improve the enzymatic activity via the proximity effect. To evaluate the feasibility of Cgk16A-CBM92 as a tool in the in situ investigation of carrageenan, a fluorescent probe was constructed by fusing Cgk16A-CBM92 with a green fluorescent protein. The in situ visualization of carrageenan in red alga Kappaphycus alvarezii was realized by utilizing the fluorescent probe [1].

Members of the CBM92 family are present in different glycoside hydrolase (GH) family sequences, e.g., GH16_17, GH5_54, GH19, and GH95. According to the CAZy database, these GH families comprise enzymes with various substrate specificities, including κ-carrageenase (GH16_17), chitinase (GH19), fucosidase (GH95), and galactosidase (GH95). It indicated that functional diversity might be present within the CBM92 family.

Family Firsts

First Identified

The first characterized CBM92 member [1] is a component of the κ-carrageenase Cgk16A [2], which was discovered from a marine bacterium Wenyingzhuangia aestuarii OF219.

First Structural Characterization

No three-dimensional structure has been solved in this CBM family at present.

References

1. Mei X, Chang Y, Shen J, Zhang Y, Han J, and Xue C. (2022). Characterization of a Novel Carrageenan-Specific Carbohydrate-Binding Module: a Promising Tool for the In Situ Investigation of Carrageenan. J Agric Food Chem. 2022;70(29):9066-9072. DOI:10.1021/acs.jafc.2c03139 |
2. Shen J, Chang Y, Chen F, and Dong S. (2018). Expression and characterization of a κ-carrageenase from marine bacterium Wenyingzhuangia aestuarii OF219: A biotechnological tool for the depolymerization of κ-carrageenan. Int J Biol Macromol. 2018;112:93-100. DOI:10.1016/j.ijbiomac.2018.01.075 |