Editing Β-Galactosidase (section)

== Species distribution ==
Much of the work done on β-galactosidase is derived from ''E. coli.'' However the enzyme can be found in many plants (especially fruits), mammals, yeast, bacteria, and fungi.<ref>{{Cite journal| vauthors = Richmond ML, Gray JI, Stine CM |date=1981|title=β-Galactosidase: Review of Recent Research Related to Technological Application, Nutritional Concerns, and Immobilization|journal=Journal of Dairy Science|volume=64|issue=9|pages=1759–1771|doi=10.3168/jds.s0022-0302(81)82764-6|issn=0022-0302|doi-access=free}}</ref> β-galactosidase genes can differ in the length of their coding sequence and the length of proteins formed by amino acids.<ref name = "Guo_2018">{{cite journal| vauthors = Guo S, Song J, Zhang B, Jiang H, Ma R, Yu M |date=2018|title=Genome-wide identification and expression analysis of β-galactosidase family members during fruit softening of peach [''Prunus persica'' (L.) Batsch] |journal=Postharvest Biology and Technology|volume=136|pages=111–123|doi=10.1016/j.postharvbio.2017.10.005 }}</ref> This separates the β-galactosidases into four families: GHF-1, GHF-2, GHF-35, and GHF- 42.<ref name="Rojas_2004">{{cite journal | vauthors = Rojas AL, Nagem RA, Neustroev KN, Arand M, Adamska M, Eneyskaya EV, Kulminskaya AA, Garratt RC, Golubev AM, Polikarpov I | display-authors = 6 | title = Crystal structures of β-galactosidase from ''Penicillium'' sp. and its complex with galactose | journal = Journal of Molecular Biology | volume = 343 | issue = 5 | pages = 1281–92 | date = November 2004 | pmid = 15491613 | doi = 10.1016/j.jmb.2004.09.012 }}</ref> ''E. Coli'' belongs to GHF-2, all plants belong to GHF-35, and ''[[Thermus thermophilus]]'' belongs to GHF-42.<ref name="Rojas_2004" /><ref name = "Guo_2018" /> Various fruits can express multiple β-galactosidase genes. There are at least seven β-galactosidase genes expressed in tomato fruit development, that have amino acid similarity between 33% and 79%.<ref>{{cite journal | vauthors = Smith DL, Gross KC | title = A family of at least seven β-galactosidase genes is expressed during tomato fruit development | journal = Plant Physiology | volume = 123 | issue = 3 | pages = 1173–83 | date = July 2000 | pmid = 10889266 | doi = 10.1104/pp.123.3.1173 | pmc = 59080 | url = }}</ref> A study targeted at identifying fruit softening of peaches found 17 different gene expressions of β-galactosidases.<ref name="Guo_2018" /> The only other known crystal structure of β-galactosidase is from ''[[Thermus thermophilus]].'' <ref name="Rojas_2004" />