Agarase

Agarase is an enzyme found in agarolytic bacteria and is the first enzyme in the agar catabolic pathway [cite journal |author=Parro V, Mellado RP |title=Effect of glucose on agarase overproduction in Streptomyces. |journal= Gene |volume=145|issue=1 |pages=49-55 |year=1994] . It is responsible for allowing them to use agar as their primary source of Carbon and enables their ability to thrive in the ocean.

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 [cite journal |author=Hassairi I, Ben Amar R, Nonus M, Gupta BB |title=Production and separation of α-agarase from "Altermonas agarlyticus" strain GJ1B. |journal= Bioresource Technology |volume=79|issue=1 |pages=47-51|year=2001] .

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 [cite journal |author=Hozoda A, Sakai M, Kanazawa S |title=Isolation and characterization of Agar-degrading "Paenibacillus" spp. Associated with the Rhizosphere of Spinach |journal= Bioscience, Biotechnology, Biochemistry |volume=67|pages=1048-1055|year=2003] ). From species within genus "Vibrio"cite journal |author=Aoki T, Araki T, Kitamikado M |title=Purification and characterization of a novel β-agarase from "Vibrio" sp. AP-2 |journal= European Journal of Biochemistry |volume=187|issue=2 |pages=461-465|year=1990] to "Alteromonas"cite journal |author=Leon O, Quintana L, Peruzzo G, Slebe JC |title=Purification and Properties of an Extracellular Agarase from "Alteromonas" sp. Strain C-1 |journal= Applied and Environmental Microbiology |volume=58|issue=12 |pages=4060-4063|year=1992] , 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. 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 [cite journal |author=Parro V, Mellado RP, Harwood CR |title=Effects of phosphate limitation on agarase production by "Streptomyces lividans" TK21 |journal= FEMS Microbiology Letters|volume=158|issue=1 |pages=107-113 |year=1998] . 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.

ee also

*Bacteria
*Agar

References