Overview:

Tri-peptidechloromethylketoneshavebeenutilizedextensivelytoirreversIBLyinhibitvariousserineproteases(1-5).AmongthemostcommonchloromethylketonesareFPRCK(Phe-Pro-Arg-chloromethylketone;commonlyreferredtoasPPACK),whichisarapidthrombininhibitorandEGRCK(Glu-Gly-Arg-chloromethylketone;commonlyreferredtoasGGACK),whichisarapidfactorXainhibitor(1).BothFPRCKandEGRCKareusedextensivelyduringproteinisolationprocedurestoinhibitserineproteaseactivityandpreventfurtherconversionofzymogenstoactiveenzymes.Recently,themodificationofthesetri-peptidechloromethylketoneswithreportinggroups,suchasfluorescentprobes(6-8,14),rADIoactivelabels(9)orthioreactive-labels(10),hasprovidedauniqueapproachtothestudyofvariousserineproteases.Theseprobesareusefulbecausetheyallowameansofreportingmolecularchangesinanenzyme,andnotitszymogen,whilealsoinhibitingtheenzymaticactivity.

TheuseofbiotinasareportinggrouphasbeenusedextensivelywithantibodiesinELISAbasedassaysandinwesternblotting.Thebiotin,inconjunctionwithavidin,createsahighlysensitivemethodfordetectingantibodies,andtherefore,antigens.Bymodifyingthetripeptide-chloromethylketoneswithabiotingroup,thesensitivityoftheavidin/biotinsystemcanbeextendedtostudyserineproteaseswithouttheneedforspecificantibodiestotheactiveenzymes.

Biotinylatedtripeptidechloromethylketonescanbeusedinavarietyofways(11-13).First,thecompoundscanbereactedwithunwantedserineproteasesinasampleorpreparation,andcanthenberemovedalongwiththeproteaseusingavidin-Sepharose(11).Second,thebiotinylated-serineproteasecanbevisualizedonablotwithouttheuseofspecificantibodies(11).Third,thebiotinylatedserineproteasecanbequantitatedinanactive-sitespecificimmunoassay(12,13,15),suchasthetPA-CASSIA(seeAssayKits).ThespacerutilizedonthesecompoundshasbeenoptimizedtoallowgoodreactivityofthebiotinylatedFPRCKandthebiotinylatedEGRCKintheabovementionedprocedures.

Inadditiontobiotinylatedchloromethylketones,fluoresceinlabelledcompoundsarealsoavailable.ThefluoresceinlabelledcompoundsareusefulinbothWesternblotandfluorescentimagingapplications.

BiotinylatedandfluoresceinlabelledFPRCKandEGRCKarepreparedbythemethodofWilliamsetal.(11).

Properties:

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