HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Chung, S. I. Articles by Folk, J. E. Search for Related Content PubMed PubMed Citation Articles by Chung, S. I. Articles by Folk, J. E. Social Bookmarking                      What's this?

Mechanism of the Inactivation of Guinea Pig Liver Transglutaminase by Tetrathionate

From the ¹ From the Laboratory of Biochemistry, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland 20014

Treatment of transglutaminase with 2 moles of sodium tetrathionate results in almost complete losses in the transferase and hydrolysis activities of the enzyme toward the substrate, benzyloxycarbonyl-l-glutaminylglycine. The calcium-dependent esterase activity of transglutaminase toward p-nitrophenyl acetate is only partially lost as a result of this treatment. A change in the mechanism of calcium activation, however, is evident from the relationship of the velocities of ester hydrolysis to metal ion concentrations. The losses in the catalytic activities of transglutaminase are accompanied by a concomitant disappearance of four sulfhydryl groups in the enzyme protein. Enzyme inactivated with ³⁵S-labeled tetrathionate showed incorporation of only small amounts of isotope, equivalent to 0.1 to 0.15 mole per mole of enzyme protein. This is in accord with evidence that the loss of the four —SH groups is the result of formation of two intramolecular disulfide bridges. Peptide mapping studies show that a single —SH group of transglutaminase previously identified as essential for all catalytic activities is not a component of the disulfide bridges formed by tetrathionate treatment. Brief incubation of the modified enzyme with dithiothreitol reduces one of these two disulfide bonds as evidenced by the recovery of two —SH groups. No restoration of enzymatic activities, however, accompanies this disulfide cleavage. Upon continued incubation with dithiothreitol, the remaining two —SH groups are recovered together with a parallel restoration of all enzymatic activities. It would appear that the catalytic changes which occur as a result of tetrathionate treatment are associated with formation of a single intramolecular disulfide bridge in the enzyme protein.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				E. Candi, G. Melino, G. Mei, E. Tarcsa, S.-I. Chung, L. N. Marekov, and P. M. Steinert Biochemical, Structural, and Transglutaminase Substrate Properties Of Human Loricrin, the Major Epidermal Cornified Cell Envelope Protein J. Biol. Chem., November 3, 1995; 270(44): 26382 - 26390. [Abstract] [Full Text] [PDF]