Exam III FAll 09

Exam III FAll 09 - V cfw_ame: Ctl*t43 cfw_0*8i*chenrlstryX...

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V{ame: , ^lt^ Ctl*t4 3{0*8i*chenrlstry Xl fixam 3 Hovember 20, ?.OAq I iart J: Multiple dhsires.for Q*estrion s I-22, cfra$serhe single best answer. 2 ptq' eaelr- : ! S Wnicn of the foll*wing ap;lroaches ls usefirl in determining the catalytic nnechanislrl of *n enzlme? a) kinetic characterization' t3] rtructural arralYsis. c) mutaticnal analY*is. @^,bandc. Zf *ernechanism of the serine proteases may be written as E + S tr* e '* 1-t ?2'+E + P2 Pl In this mechanisnr" the intermediate [*Pt is: al the non-eovalerlt enzyrne-subfirate cornplex. bl the transitisn state. @ the acYl-enzYrne intermediate' ;,t the non-covaient enzynre-product eomplex' N Xo*e were ro measure the pl-t depende*ce of k".* fr:r ehymotrypsin, one woufd 1ryqct:-q,1t,k" *?y-ldt "' f.,ffi"';;;;;;ie with increaring pH unti! it reaches a maximum at epprsxirnately pH s and then relilain \"/ constant pH values greater than B' b) remain csnstant with i'rcreasing pH' bcrease athiglrer pFi.valu*s {pl{ a c] rernaisr eonstant with inereasinfi pFl for iow pH values and then decrease at htgf]er' p v > 8i" ""i+f* ^rJ {nr lnt*r n!{ t}s}tt,,q'rrntit ii nea nd ther* decfeate at higher pFt *2 increa*e with pH fclr trow pH value* {rfitil a maximurn a values. ./i lnthe nrechanisn'l af serine proteales, which residue acts aa the rrucleaphilef A*p-"tr07 Ser-195 Asp-l5? Ser-57 a) w di p,{ lf************************************n€ were t0 mea$rrr* the pH dependenre at llK$for chymotrpsin, one wtltlld expeqtt'hat llK* , ,, $.i*rease with increasing pH until it reaclres a nnaxin':urn at approxirnately pl-t s a*dtlen're3?'ffiin' c$fistant al pl-'l values.greater.thran 8' bl remain pH. ffi',1*"^r; ;;;;;t wirh increarinf pH f$r luw pt-{ values arrd at high*r pl-* values {pfi ; ;:l-rr. rvith pH for low pH vatues until it reaches a rnaximum at pH I and then decrease at higher pl-l vafues. , { Arnaior differencgin the gy11 a*d$s2 mod*ls-fcr the kinetic r*eehanirn'l *f lysczyrne ir: O' a) residue 35 dd; n*t have tc be pr*tnnated in the S*? model E b) residue 35 has to be pratonated in the S*2 model' cL the S*I nrodel involves the farmation of a ccvalerrt intermediate. @il- ili ;;;;, i"""rr-, tr.,* i"r*ution of a covarent *s*fa'a*jog*blaa*dsrtisfgingFrplSrhrrr'Lsgivirugt t+*va ,.,ir
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1 f lLii!-ll."i, polyrner was used a* a substrate for tysczynre. tf r*sidue F of the polynrer was situarec lle ihe first binding site r:f l*rn*zyme, the bonc* hetween which rnvs resirjues worrld be cieavcdl a) 7 andS , @ rands c) I and 7A d) ?oand 11 {, n &l' Ane argum€nt agair.r*t the S*? mechanisnr is that; a} there il n{} evldence suppr:rting the pr*pured role of water in the 5"'! rnecha6iEm. .* {l*:yate r*sidues are *,,r usu*fiy prroto*ared *r g:hysr*}cgical pH" q, tle lifetirne of the prcptised ca&ccati*nic iritermediat* woufd'be t*a chsd ta be ecnsist€*t with the observations. /1:', {9j the prcposer* r:"1*char:isnr is based on experirnenfs that invrlved a mutant versicn of tire en;yme. &T tn order lcr a che*rleal reacticln tn be therm*dynanrically f*vorable: aj .trH nr*ct be greater than &S" .*, 45 must be greater than AH. @) -f AS nrusr be greater di &l-* rnuEt be greater than T&S. .d'- "i"u) An endergr:nic reaction is one in lvhich: C.p,oruro { C,u".*ne trt fi**rnn* Cu*'*. c) Cp*a* = C*ra"nb. ) dl Cp*o* 5 C**n* j4'; &* er:cl*thermic
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Exam III FAll 09 - V cfw_ame: Ctl*t43 cfw_0*8i*chenrlstryX...

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