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 Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Dhawan, S. Articles by Fleming, P. J. Search for Related Content PubMed PubMed Citation Articles by Dhawan, S. Articles by Fleming, P. J. Social Bookmarking                      What's this?

J. Biol. Chem., Vol. 261, Issue 17, 7680-7684, Jun, 1986

Adenosine 5'-diphosphate-dependent subunit dissociation of bovine dopamine beta-hydroxylase

S Dhawan, P Hensley, JC Osborne Jr and PJ Fleming

In a previous study, it was shown that purified soluble bovine dopamine beta-hydroxylase exhibits pH-dependent reversible tetramer-dimer dissociation (Saxena, A., Hensley, P., Osborne, J. C., Jr., and Fleming, P. J. (1985) J. Biol. Chem. 260, 3386-3392). Here we report evidence for the dissociation of this enzyme by magnesium-adenosine diphosphate independent of pH in the pH range 5-7. Quantitative binding of ADP to dopamine beta-hydroxylase revealed that there are two binding sites/dimeric species of hydroxylase and that ADP is tightly bound with a KD less than 10(-8) M. Kinetic data obtained at pH 5.5, the pH inside the chromaffin granule, shows that the apparent Km values for both the substrates tyramine and ascorbate are lowered by the presence of ADP without affecting the Vmax of the enzyme. The ADP-dependent lowering of apparent Km values results from a dissociation of the enzyme to the dimeric species which has inherently lower apparent Km values for substrates.
CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?