Agarase

Related Reading

The system name of agarase is agarose 4-glycosyl hydrolase. It is found in agar-decomposing bacteria and is the first enzyme in the agar-catabolism pathway. It is responsible for enabling them to use agar as their main carbon source and enabling them to thrive in the ocean. According to whether agarase degrades the α or β bonds in agarose, the agarose is broken down into oligosaccharides and divided into α-agarose or β-agarose. When secreted, the oligosaccharides produced by α-agarose have 3.6 anhydro-L-galactose at the reducing end, while β-agarose produces D-galactose residues.

Figure 1. Protein structure of agarase.

Classifications

Agarase that can degrade agar can be isolated from the ocean and other environments. According to different modes of action, agarase can be divided into two types: α-agarose and β-agarose. Different agarases have different biological characteristics. Agarase has important application value in the preparation of seaweed single cells, the preparation of seaweed protoplasts, the preparation of agar-oligosaccharides, the study of seaweed polysaccharide structure and molecular biology research.

Mechanism

According to the substrate specificity of lyase, the mechanism of agarase is divided into two types:

The first mechanism originated from the study of β ATCC 19292-agarase from Pseudoalteromonas atlantica. Endo-type β agarase I in this bacteria

Breaking the β-linked-(EC3.2.1.81)-(1,4) agar polymer produces a mixture of oligosaccharides, with new agarotetraose as the main product. Then these oligosaccharides are hydrolyzed by the exo-type β Sepharase II bound by the membrane to generate new agarobiose. Finally, the new agarobiose is hydrolyzed by the new agarobiose water in the cytoplasm, and hydrolyzed into the internal ether L-galactose and galactose 3, 6.

The second mechanism is that the extracellular α-agarose enzyme breaks the α-linked agarose--(1, 3). Produce oligosaccharides with new agarobiose as the unit, and produce D-galactose at the non-reducing end.

α-Agarase

So far, only a few kinds of alpha agarase have been studied and reported. In 1978, an agarase was isolated from a Gram-negative marine bacterium. This enzyme is precipitated by ammonium sulfate, DEAE-13-NMR cellulose column for purification. Paper chromatography proved that the hydrolysate contained agarose and agarose.

β-Agarase

β-Agarase cleaves agarose subunits or unsubstituted new agarose (3,6-anhydride-α-L-galactosyl-1-3-D-galactose) to generate new agar-oligos sugar. β-Agarase I digests agarose, forming carbohydrate molecules that can no longer gel, and at the same time releases the captured DNA. Normally, residual carbohydrate molecules or β-Sepharose I will not affect the subsequent DNA operations such as restriction enzyme digestion, ligation reaction and transformation reaction.

Applications

• Used as a tool enzyme for enzymatic hydrolysis of seaweed

Since agar is an important component of some red algae cell walls, agarase can be used as a tool enzyme for enzymatic hydrolysis of large seaweeds to obtain single cells or protoplasts. Most of the seaweed wall-lysis enzymes used in the past were isolated and prepared from the digestive system of marine animals

• Applications in molecular biology

The use of agarase to recover and from agarose gels has proven to be one of the best methods.

• For the preparation of agar-oligosaccharides

Agar can be hydrolyzed by agarase to form oligosaccharides such as trisaccharide and tetrasaccharide. Agar-oligosaccharides have a wide range of applications in food production. It can be used in the production of beverages, bread and some low-calorie foods.

• Used in the study of seaweed polysaccharide structure

It is an effective method to hydrolyze the polysaccharides of some seaweeds with agarase to determine the structure of the hydrolysate, and then to infer the structure of the polysaccharides.

References

1. Groleau D.; et al. Enzymatic hydrolysis of agar:purification and characterization of beta neoagarotetraose hydrolase from Pseudomonas atlantica. Can J Microbiol, 1977, 23(6): 672-697.
2. Bibb M J.; et al. The agarase gene(dag A) of Streptomyces coelicolor A3(2): affinity purification and characterization of the cloned gene product. J Gen Microbiol, 1987, 133(Pt 8):2 089-2 096.