Pectatelyase10A(Pel10A)enzymefrom
Pseudomonascelluloseiscomposedof649residuesandhasamolecularmassof68.5kDa.SequenceanalysisrevealedthatPel10Acontainedasignalpeptideandtwoserine-richlinkersequencesthatseparatethreemodules.Sequencesimilaritywasseenbetweenthe9.2kDaN-terminalmoduleofPel10Aandfamily2acarbohydrate-bindingmodules(CBMs).ThisN-terminalmoduleofPel10Awasshowntoencodeanindependentlyfunctionalmodulewithaffinitytocrystallinecellulose.Ahighsequenceidentityof66%wasseenbetweenthe14.2kDacentralmoduleofPel10Aandthefunctionallyuncharacterizedcentralmodulesofthexylan-degr
ADIngenzymesendoxylanase10B,ar
ABInofuranosidase62Candesterase1D,alsofrom
P.cellulosa.The35.8kDaC-terminalmoduleofPel10Awasshowntohave30and36%identitieswiththefamily10pectatelyasesfrom
Azospirillumirakenseandanalkaliphilicstrainof
Bacillussp.strainKSM-P15,respectively.ThisHis-taggedC-terminalmoduleofthePel10Awasshowntoencodeanindependentcatalyticmodule(Pel10Acm).Pel10Acmwasshowntocleavepectateandpectininanendo-fashionandtohaveoptimalactivityatpH10andinthepresenceof2mMCa
2+.Highestenzymeactivitywasdetectedat62°C.Pel10Acmwasshowntobemostactiveagainstpectate(i.e.polygalacturonicacid)withprogressivelylessactivityagainst31,67and89%esterifiedcitruspectins.ThesedatasuggestthatPel10Ahasapreferenceforsequencesofnon-esterifiedgalacturonicacidresidues.Significantly,Pel10Aandthe
P.celluloserhamnogalacturonanlyase11A,intheaccompanyingarticle[McKie,Vincken,Voragen,vandenBroek,StimsonandGilbert(2001)Biochem.J.355,167–177],arethefirstCBM-containingpectinasesdescribedtodate.