<b>Evidence for Conformational Changes in α-Chymotrypsin-catalyzed Reactions. VI. Changes in Optical Rotatory Dispersion Parameters</b>

Havsteen, B.; Hess, George P.

doi:10.1021/ja00889a029

Cited by 45 publications

(13 citation statements)

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“…Conformational Change of Ac-CT at Alkaline p H It has been suggested on the basis of optical rotation changes that chymotrypsin [36] and Ac-CT [17] undergo a change in conformation between pH 7 and pH 11. This change has been reinvestigated in the present study in order to ascertain how it correlates with ionization of tyrosine and/or with ionization of the group that controls the activity.…”

Section: Rate Of Deacetylation Of Tyrosinesmentioning

confidence: 99%

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Study of the Groups Controlling the Activity and Conformation of Chymotrypsin at Alkaline pH: N‐Terminal Isoleucine and Tyrosines

Karibian¹,

Laurent²,

Labouesse³

et al. 1968

European Journal of Biochemistry

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It is shown that the change in activity and structure of acetyl-6-chymotrypsin in the pH 7-11 range is not correlated with the ionizations of tyrosine residues.The pKs of the two titratable tyrosines of acetyl-8-chymotrypsin are found to be 10.2 and 11.5, a t 15' (9.6 and 10.8 after correction for electrostatic interactions), and those of the starting acetylated zymogen are 10.5 and 12.1 (10.0 and 11.5 after identical corrections). The plot of log rate of deacetylation of the titratable tyrosines versus pH is linear between pH 9 and pH 12. At a given pH there is a linear relation between the log deacetylation rate and the pKs of the residues. The pH rate profile of acylation of acetyl-8-chymotrypsin by 4-carboxy-3-nitrophenyl-N,N-diphenylcarbamate is bell-shaped, with a maximum a t pH 7.9 a t 15", in 0.14 M KC1. The right side of the curve shows a pKapp of 8.9, whether the exposed titrable tyrosines of the enzyme are acetylated or not. A similar pKapp (9.1) is found for the pH-dependent change in optical rotation of the acetylated enzyme, when the exposed tyrosines are acetylated. After correction for electrostatic interactions, this apparent pK becomes 8.4 and can be assigned only to the a-aminogroup of the N-terminal isoleucine.Recently, conflicting reports have been presented on the role [l --31 of the two exposed tyrosine residues in chymotrypsin, and on their ionization state [4-71. Values of pK ranging from 9.1 [4,7] to 10.6 [5] have been assigned to them. Considerable evidence has shown that a n ionizable group of p K about 9 is involved in the control of activity [8-111 and structure [12-151 of chymotrypsin. With this evidence and the X-ray work of Matthews et al. [16], it seemed useful to examine how tyrosine ionization is involved in the active conformation of the protein and how it interferes with that of the N-terminal isoleucine residue of the B chain of the enzyme. The latter amino acid has emerged recently as the most probable residue controlling chymotrypsin activity a t alkalineThe work reported here was carried out using acetylated 8-chymotrypsin (Ac-CT), made by activation of acetylated chymotrypsinogen (Ac-CTG) pH [17-191. Non-Standard Abbreviations. Ac-Tyr-OEt, N-acetyl-Ltyrosine ethylester ; DPCC diphenylcarbamyl chloride; NCDC, 4-carboxy-3nitrophenyl-N,N-diphenylcarbamate; Ac-Tyr-NH,, N-acetyl-L-tyrosinamide; Ac,-Tyr-NH,, N,Odiacetyl-L-tyrosinamide ; Ac-CTG, refers to chymotrypsinogen with all of its s-NH, groups of lysine and its a-NH, group of half-cystine acetylated; Ac-CT, refers to S-chymotrypsin obtained from Ac-CTG. When specified -Tyr(H) refers to proteins whose exposed tyrosines are free to ionize ; -Tyr(Ac) refers to proteins whose exposed tyrosines are acetylated.Enzymes. Chymotrypsin (EC 3.4.4.5) ; trypsin (EC 3.4.4.4).[17], so that the results would not be obscured by lysine or N-terminal half-cystine ionizations. Previous results [17] have shown that the €-amino groups of lysine residues and the a-amino group of N-terminal half-cystine are not related to the decrease in ...

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Section: Rate Of Deacetylation Of Tyrosinesmentioning

confidence: 99%

“…phosphoryl derivative are essentially fixed over the same pH range [36,56]. It has been shown that the change in structure of the enzyme is associated with the deprotonation of one ionizable group [I71 postulated to be theN-terminal isoleucine [19].…”

Section: Relationship Between Tyrosine Ionization Andmentioning

confidence: 99%

Study of the Groups Controlling the Activity and Conformation of Chymotrypsin at Alkaline pH: N‐Terminal Isoleucine and Tyrosines

Karibian¹,

Laurent²,

Labouesse³

et al. 1968

European Journal of Biochemistry

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“…Additionally, such information may shed light on the interactions among different neurochemicals. For example, if carbachol does become associated with the axon, it may subsequently cause the release of the transmitter located in the end button of the axon (13). This view might explain the occurrence of 2to 5minute latencies of behavioral effects which are sometimes observed after chemical stimulation of the brain.…”

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confidence: 99%

Conformation and Activity of Chymotrypsin: The p H-Dependent, Substrate-Induced Proton Uptake

McConn

Odell

et al. 1968

Science

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Hydrogen ion uptake by chymotrypsin during reversible binding of specific substrate is shown to be due to an ionizing group of the enzyme with a pK(apparent) approximately 9 in the free enzyme. This pK(apparent) is shifted to higher value in the enzyme-substrate complexes. Previous results indicating an equilibrium, controlled by this ionizing group, between active and inactive conformational forms of chymotrypsin are confirmed.

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“…Work-up as in A gave 3.4 g of distilled product which was pure e«cfo-bicyclo[3.2.1]oct-6-en-8-yl acetate (9). e/iífo-Bicyclo[3.2.1]oct-6-en-8-ol (11). A solution of 3.8 g of 9 in 60 ml of ether was added to a stirred slurry of 1.0 g of lithium aluminum hydride and 200 ml of ether over 30 min.…”

Section: Methodsmentioning

confidence: 99%

“…Reduction of 9 with lithium aluminum hydride gave e«úfo-bicyclo[3.2.1]oct-6-en-8-ol (11), which when treated with tosyl chloride in pyridine afforded the crystalline e«i/o-bicyclo[3.2.1]oct-6-en-8-yl tosylate (4).…”

mentioning

confidence: 99%

Solvolytic reactions of endo-bicyclo[3.2.1]oct-6-en-8-yl tosylate

Hess¹

1971

J. Am. Chem. Soc.

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The rates of solvolysis of endo-bicyclo[3.2.1]oct-6-en-8-yl tosylate have been determined in acetic acid and ethanol-water mixtures. Product studies indicated that only products with the parent structure were formed. Both the results of product studies and interpretation of rate data support a significant amount of anchimeric assistance by the carbon-carbon double bond.the known ezzz/o-bicyclo[3.2.1]octan-8-ol.10 The nmr spectrum of 9 had absorptions at 4.13 (m, 2, CH=CH), 5.25 (t, 1, CHOAc), 7.48 (m, 2, bridgehead), 7.94 (s, 3, CH3), 8.20-9.08 (general absorption, 6, (CH2)3). At normal sweep width the vinyl region of 9(5) The synthesis and solvolytic behavior of a related compound, endobicyclo[3.2.1]octa-2,6-dien-8-yl tosylate, has been reported: G. Klump,

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Evidence for Conformational Changes in α-Chymotrypsin-catalyzed Reactions. VI. Changes in Optical Rotatory Dispersion Parameters

Cited by 45 publications

References 4 publications

Study of the Groups Controlling the Activity and Conformation of Chymotrypsin at Alkaline pH: N‐Terminal Isoleucine and Tyrosines

Study of the Groups Controlling the Activity and Conformation of Chymotrypsin at Alkaline pH: N‐Terminal Isoleucine and Tyrosines

Conformation and Activity of Chymotrypsin: The p H-Dependent, Substrate-Induced Proton Uptake

Solvolytic reactions of endo-bicyclo[3.2.1]oct-6-en-8-yl tosylate

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