Agarase

Agarase (EC 3.2.1.81, AgaA, AgaB, endo-beta-agarase, agarose 3-glycanohydrolase) is an enzyme with systematic name agarose 4-glycanohydrolase. It is found in agarolytic bacteria and is the first enzyme in the agar catabolic pathway.[1] It is responsible for allowing them to use agar as their primary source of Carbon and enables their ability to thrive in the ocean.

Beta-agarase
Identifiers
EC number3.2.1.81
CAS number37288-57-6
Databases
IntEnzIntEnz view
BRENDABRENDA entry
ExPASyNiceZyme view
KEGGKEGG entry
MetaCycmetabolic pathway
PRIAMprofile
PDB structuresRCSB PDB PDBe PDBsum

Agarases are classified as either α-agarases or β-agarases based upon whether they degrade α or β linkages in agarose, breaking them into oligosaccharides. When secreted, α-agarases yield oligosaccharides with 3.6 anhydro-L-galactose at the reducing end whereas β-agarases result in D-galactose residues.[2]

Function in Environment

As could be expected, many species of agar-degraders are marine micro-organisms – an adaptation to their environment which would be wasted in the majority of micro-organisms existing on land (although there are such examples, including a species of Paenibacillus in the Rhizosphere of Spinach[3]). From species within genus Vibrio[4] to Alteromonas,[5] the presence of agarase allows agar-degrading bacteria an abundant food source in the ocean. Research also demonstrates that glucose can inhibit extracellular agarase secretion (but not transcription), causing it to degrade within the cell and thus limit growth of the bacteria.[5] In addition, a study of the effects of phosphate limitation on agarase shows that limiting phosphate increases both intracellular agarase production and extracellular secretion, whereas a magnesium limitation does not.[6] This further highlights the niche which this class of bacteria usually occupies, as the concentration of glucose or phosphate in the ocean is very low while magnesium concentration is generally much higher, suiting the agar-degrading bacteria’s agarase production; there is simply no need to use glucose in the ocean, so many organisms don't.

While the optimal pH of agarase is 5.5, it is stable at a tolerant range, from 4.0 to 9.0.[4]

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See also

References
  1. Parro V, Mellado RP (1994). "Effect of glucose on agarase overproduction in Streptomyces". Gene. 145 (1): 49–55. doi:10.1016/0378-1119(94)90321-2. PMID 8045423.
  2. Hassairi I, Ben Amar R, Nonus M, Gupta BB (2001). "Production and separation of α-agarase from Altermonas agarlyticus strain GJ1B". Bioresource Technology. 79 (1): 47–51. doi:10.1016/S0960-8524(01)00037-2. PMID 11396907.
  3. Hozoda A, Sakai M, Kanazawa S (2003). "Isolation and characterization of Agar-degrading Paenibacillus spp. Associated with the Rhizosphere of Spinach". Bioscience, Biotechnology, and Biochemistry. 67 (5): 1048–1055. doi:10.1271/bbb.67.1048.
  4. Aoki T, Araki T, Kitamikado M (1990). "Purification and characterization of a novel β-agarase from Vibrio sp. AP-2". European Journal of Biochemistry. 187 (2): 461–465. doi:10.1111/j.1432-1033.1990.tb15326.x. PMID 2298219.
  5. Leon O, Quintana L, Peruzzo G, Slebe JC (1992). "Purification and Properties of an Extracellular Agarase from Alteromonas sp. Strain C-1". Applied and Environmental Microbiology. 58 (12): 4060–4063. PMC 183228. PMID 16348832.
  6. Parro V, Mellado RP, Harwood CR (1998). "Effects of phosphate limitation on agarase production by Streptomyces lividans TK21". FEMS Microbiology Letters. 158 (1): 107–113. doi:10.1111/j.1574-6968.1998.tb12808.x.
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