関: beta-gal、lactase

WordNet

any of a group of enzymes (trade name Lactaid) that hydrolyze lactose to glucose and galactose (同)Lactaid
to remain unmolested, undisturbed, or uninterrupted -- used only in infinitive form; "let her be"
work in a specific place, with a specific subject, or in a specific function; "He is a herpetologist"; "She is our resident philosopher" (同)follow
have life, be alive; "Our great leader is no more"; "My grandfather lived until the end of war" (同)live
be identical to; be someone or something; "The president of the company is John Smith"; "This is my house"
happen, occur, take place; "I lost my wallet; this was during the visit to my parents house"; "There were two hundred people at his funeral"; "There was a lot of noise in the kitchen"
have the quality of being; (copula, used with an adjective or a predicate noun); "John is rich"; "This is not a good answer"
occupy a certain position or area; be somewhere; "Where is my umbrella?" "The toolshed is in the back"; "What is behind this behavior?"
spend or use time; "I may be an hour"
stake on the outcome of an issue; "I bet $100 on that new horse"; "She played all her money on the dark horse" (同)wager, play
the act of gambling; "he did it on a bet" (同)wager
maintain with or as if with a bet; "I bet she will be there!" (同)wager
second in order of importance; "the candidate, considered a beta male, was perceived to be unable to lead his party to victory"
the 2nd letter of the Greek alphabet
preliminary or testing stage of a software or hardware product; "a beta version"; "beta software"
beets (同)genus Beta

PrepTutorEJDIC

《連結語として補語を伴なって…『である』,…だ,…です / 《位置・場所を表す語句を伴って》(…に)『ある』,いる(occupy a place or situation) / 〈物事が〉『存在する』,ある(exist);〈生物が〉生存する,生きている(live) / 行われる,起こる,発生する(take place, occur) / 存続する,そのままでいる(remain as before) / 《『be to』 do》 / …する予定である,…することになっている / …すべきだ / 《受動態の不定詞を伴って》…できる / 《命令》…するのだ / 《条件節に》…する意図がある / 《『if…were to』 do》…するとしたなら / 《『be』 do『ing』》《進行形》 / 《進行中の動作》…している,しつつある / 《近い未来》…しようとしている,するつもり / 《動作の反復》(いつも)…している / 《『be』+『他動詞の過去分詞』》《受動態》…される,されている / 《『be』+『自動詞の過去分詞』》《完了形》…した[状態にある]
『かけ』・(…との)かけ《+『with』+『名』》 / かけた物(金) / かけの対象 / 〈金・物〉'を'『かける』 / (かけ事・ゲームなどで)〈人〉‘と'『かけをする』《+『名』〈人〉+『on』+『名』》 / (…に)『かける』《+『on』(『against』)+『名』(one's do『ing』)》
ベータ(ギリシア語アルファベットの第2文字;B,β;英語のB,b に遭当)

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/06/09 08:54:44」(JST)

wiki en

β-galactosidase, also called beta-gal or β-gal, is a hydrolase enzyme that catalyzes the hydrolysis of β-galactosides into monosaccharides. Substrates of different β-galactosidases include ganglioside GM1, lactosylceramides, lactose, and various glycoproteins.^[1]

Properties and functions

β-galactosidase is an exoglycosidase which hydrolyzes the β-glycosidic bond formed between a galactose and its organic moiety. It may also cleave fucosides and arabinosides but with much lower efficiency. It is an essential enzyme in the human body. Deficiencies in the protein can result in galactosialidosis or Morquio B syndrome. In E. coli, the gene of β-galactosidase, the lacZ gene, is present as part of the inducible system lac operon which is activated in the presence of lactose when glucose level is low.

It is commonly used in molecular biology as a reporter marker to monitor gene expression. It also exhibits a phenomenon called α-complementation which forms the basis for the blue/white screening of recombinant clones. This enzyme can be split in two peptides, LacZα and LacZΩ, neither of which is active by itself but when both are present together, spontaneously reassemble into a functional enzyme. This property is exploited in many cloning vectors where the presence of the lacZα gene in a plasmid can complement in trans another mutant gene encoding the LacZΩ in specific laboratory strains of E. coli. However, when DNA fragments are inserted in the vector, the production of LacZα is disrupted, the cells therefore show no β-galactosidase activity. The presence or absence of an active β-galactosidase may be detected by X-gal, which produces a characteristic blue dye when cleaved by β-galactosidase, thereby providing an easy means of distinguishing the presence or absence of cloned product in a plasmid.

In 1995, Dimri et al. proposed a new isoform for beta-galactosidase with optimum activity at pH 6.0 (Senescence Associated beta-gal or SA-beta-gal)^[2] which would be specifically expressed in senescence (The irreversible growth arrest of cells). Specific quantitative assays were even developed for its detection.^[3]^[4]^[5] However, it is now known that this is due to an overexpression and accumulation of the lysosomal endogenous beta-galactosidase,^[6] and its expression is not required for senescence. Nevertheless, it remains the most widely used biomarker for senescent and aging cells, because it is reliable and easy to detect.

Structure

Ribbon diagram of the 3MUY structure (tetramer), E. coli (lacZ) beta-galactosidase (R599A).^[7]

The 1,024 amino acids of E. coli β-galactosidase were first sequenced in 1970,^[8] and its structure determined twenty-four years later in 1994. The protein is a 464-kDa homotetramer with 2,2,2-point symmetry ^[9] Each unit of β-galactosidase consists of five domains; domain 1 is a jelly-roll type barrel, domain 2 and 4 are fibronectin type III-like barrels, domain 5 a β-sandwich, while the central domain 3 is a TIM-type barrel.

The third domain contains the active site.^[10] The active site is made up of elements from two subunits of the tetramer, and disassociation of the tetramer into dimers removes critical elements of the active site. The amino-terminal sequence of β-galactosidase, the α-peptide involved in α-complementation, participates in a subunit interface. Its residues 22-31 help to stabilize a four-helix bundle which forms the major part of that interface, and residue 13 and 15 also contributing to the activating interface. These structural features provide a rationale for the phenomenon of α-complementation, where the deletion of the amino-terminal segment results in the formation of an inactive dimer.

Reaction

The active site of β-galactosidase catalyzes the hydrolysis of its disaccharide substrate via "shallow" and "deep" binding. Monovalent potassium ions (K⁺) as well as divalent magnesium ions (Mg²⁺) are required for the enzyme's optimal activity. The beta-linkage of the substrate is cleaved by a terminal carboxyl group on the side chain of a glutamic acid.

In E. coli, Glu-461 was thought to be the nucleophile in the substitution reaction.^[11] However, it is now known that Glu-461 is an acid catalyst. Instead, Glu-537 is the actual nucleophile,^[12] binding to a galactosyl intermediate.

In humans, the nucleophile of the hydrolysis reaction is Glu-268.^[13]

β-galactosidase reaction

Uses

The β-galactosidase assay is used frequently in genetics, molecular biology, and other life sciences. An active enzyme may be detected using X-gal, which forms an intense blue product after cleavage by β-galactosidase, and is easy to identify and quantify. It is used for example in blue white screen.^[14] Its production may be induced by a non-hydrolyzable analog of allolactose, IPTG, which binds and releases the lac repressor from the lac operator, thereby allowing the initiation of transcription to proceed.

Since it is highly expressed and accumulated in lysosomes in senescent cells, it is used as a senescence biomarker both in vivo and in vitro in qualitative and quantitative ^[3] assays, despite its limitations.

References

^ Dorland's Illustrated Medical Dictionary. Retrieved 2006-10-22.
^ Dimri GP, Lee X, Basile G, Acosta M, Scott G, Roskelley C, Medrano EE, Linskens M, Rubelj I, Pereira-Smith O (September 1995). "A biomarker that identifies senescent human cells in culture and in aging skin in vivo". Proc. Natl. Acad. Sci. U.S.A. 92 (20): 9363–7. doi:10.1073/pnas.92.20.9363. PMC 40985. PMID 7568133.
^ ^a ^b Bassaneze V, Miyakawa AA, Krieger JE (January 2008). "A quantitative chemiluminescent method for studying replicative and stress-induced premature senescence in cell cultures". Anal. Biochem. 372 (2): 198–203. doi:10.1016/j.ab.2007.08.016. PMID 17920029.
^ Gary RK, Kindell SM (August 2005). "Quantitative assay of senescence-associated beta-galactosidase activity in mammalian cell extracts". Anal. Biochem. 343 (2): 329–34. doi:10.1016/j.ab.2005.06.003. PMID 16004951.
^ Itahana K, Campisi J, Dimri GP (2007). "Methods to detect biomarkers of cellular senescence: the senescence-associated beta-galactosidase assay". Methods Mol. Biol. Methods in Molecular Biology 371: 21–31. doi:10.1007/978-1-59745-361-5_3. ISBN 978-1-58829-658-0. PMID 17634571.
^ Lee BY, Han JA, Im JS, Morrone A, Johung K, Goodwin EC, Kleijer WJ, DiMaio D, Hwang ES (April 2006). "Senescence-associated beta-galactosidase is lysosomal beta-galactosidase". Aging Cell 5 (2): 187–95. doi:10.1111/j.1474-9726.2006.00199.x. PMID 16626397.
^ Dugdale, M.L.; et al. (2010). "Importance of Arg-599 of b-galactosidase (Escherichia coli) as an anchor for the open conformations of Phe-601 and the active-site loop". Biochem.Cell Biol. (88): 969–979. doi:10.2210/pdb3muy/pdb. rendered with PyMOL
^ Fowler AV, Zabin I (October 1970). "The amino acid sequence of beta galactosidase. I. Isolation and composition of tryptic peptides". J. Biol. Chem. 245 (19): 5032–41. PMID 4918568.
^ Jacobson, R. H.; Zhang, X. -J.; Dubose, R. F.; Matthews, B. W. (1994). "Three-dimensional structure of β-galactosidase from E. Coli". Nature 369 (6483): 761–766. doi:10.1038/369761a0. PMID 8008071. edit
^ Matthews BW (June 2005). "The structure of E. coli beta-galactosidase". C. R. Biol. 328 (6): 549–56. doi:10.1016/j.crvi.2005.03.006. PMID 15950161.
^ Gebler JC, Aebersold R, Withers SG (June 1992). "Glu-537, not Glu-461, is the nucleophile in the active site of (lac Z) beta-galactosidase from Escherichia coli". J. Biol. Chem. 267 (16): 11126–30. PMID 1350782.
^ Yuan J, Martinez-Bilbao M, Huber RE (April 1994). "Substitutions for Glu-537 of beta-galactosidase from Escherichia coli cause large decreases in catalytic activity". Biochem. J. 299 (Pt 2): 527–31. PMC 1138303. PMID 7909660.
^ McCarter JD, Burgoyne DL, Miao S, Zhang S, Callahan JW, Withers SG (January 1997). "Identification of Glu-268 as the catalytic nucleophile of human lysosomal beta-galactosidase precursor by mass spectrometry". J. Biol. Chem. 272 (1): 396–400. doi:10.1074/jbc.272.1.396. PMID 8995274.
^ Beta-Galactosidase Assay (A better Miller) - OpenWetWare

External links

beta-Galactosidase at the US National Library of Medicine Medical Subject Headings (MeSH)

UpToDate Contents

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English Journal

Synthesis and characterisation of galactosyl glycerol by β-galactosidase catalysed reverse hydrolysis of galactose and glycerol.

Wei W, Qi D, Zhao HZ, Lu ZX, Lv F, Bie X.SourceCollege of Food Science and Technology, Nanjing Agricultural University, Nanjing 210095, PR China.
Food chemistry.Food Chem.2013 Dec 1;141(3):3085-92. doi: 10.1016/j.foodchem.2013.05.145. Epub 2013 Jun 10.
A study of an enzymatic method for the production of galactosylglycerol is described. The effects of enzyme sources, enzyme amount, reaction temperature, reaction time, substrate ratio of glycerol to galactose, buffer content and pH on galactosylglycerol yield (mg/ml) were investigated. Under the op
PMID 23871063

STATISTICAL APPROACH FOR THE ENHANCED PRODUCTION OF COLD-ACTIVE β-GALACTOSIDASE FROM Thalassospira frigidphilosprofundus: A NOVEL MARINE PSYCHROPHILE FROM DEEP WATERS OF BAY OF BENGAL.

Pulicherla KK, Kumar PS, Manideep K, Rekha VP, Ghosh M, Rao KR.Sourcea Center for Bioseparation Technology , VIT University , Vellore , India.
Preparative biochemistry & biotechnology.Prep Biochem Biotechnol.2013 Nov 17;43(8):766-80. doi: 10.1080/10826068.2013.773341.
In the present investigation Thalassospira frigidphilosprofundus, a novel species from the deep waters of the Bay of Bengal, was explored for the production of cold-active β-galactosidase by submerged fermentation using marine broth medium as the basal medium. Effects of various medium constituents
PMID 23876137

Polysaccharide-based biomaterials with on-demand nitric oxide releasing property regulated by enzyme catalysis.

Zhao Q, Zhang J, Song L, Ji Q, Yao Y, Cui Y, Shen J, Wang PG, Kong D.SourceState Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Bioactive Materials, Ministry of Education, Nankai University, Tianjin 300071, PR China.
Biomaterials.Biomaterials.2013 Nov;34(33):8450-8. doi: 10.1016/j.biomaterials.2013.07.045. Epub 2013 Jul 30.
The regulatory role of nitric oxide (NO) in cell signaling has been well recognized. Clinically, NO deficiency is known to be associated with severe vascular disorders, especially in patients with long-term diabetes. Exogenous compensation of NO is a promising therapeutic strategy, although the lack
PMID 23911069

Japanese Journal

Streptococcus suis Type 2 SSU0587 Protein is a Beta-Galactosidase That Contributes to Bacterial Adhesion but Not to Virulence in Mice

Journal of Veterinary Medical Science 76(7), 1055-1059, 2014
NAID 130003391311

High cell-density expression system : A novel method for extracellular production of difficult-to-express proteins(GENETICS, MOLECULAR BIOLOGY, AND GENE ENGINEERING)

Journal of bioscience and bioengineering 113(2), 154-159, 2012-02
NAID 110009418661

Extremely Low Frequency Magnetic Fields Do Not Elicit Oxidative : Stress in MCF10A Cells

Journal of radiation research 53(1), 79-86, 2012-01-16
NAID 10030023604

Related Pictures

★リンクテーブル★

リンク元	「β-ガラクトシダーゼ」「lactase」「beta-gal」
関連記事	「beta」「be」

「β-ガラクトシダーゼ」

galactosidase, beta 1
Identifiers
Symbol	GLB1
Alt. symbols	ELNR1
Entrez	2720
HUGO	4298
OMIM	230500
RefSeq	NM_000404
UniProt	P16278
Other data
Locus	Chr. 3 p22.3

Search
PMC	articles
PubMed	articles
NCBI	proteins

β-galactosidase
	β-galactosidase from Penicillum sp.
Identifiers
EC number	3.2.1.23
CAS number	9031-11-2
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Gene Ontology	AmiGO / EGO
Search
PMC	articles
PubMed	articles
NCBI	proteins