Document Detail

The interplay between basicity, conformation, and enzymatic reduction in biliverdins.
MedLine Citation:
PMID:  1417867     Owner:  NLM     Status:  MEDLINE    
Biliverdins with extended conformations are reduced by biliverdin reductase (BvR) at higher rates than biliverdins with helical conformations. To find out the molecular basis for this important feature of BvR mechanism, helical and extended biliverdins were titrated for their acid-base equilibria in a protic solvent (methanol). It was found that the basicity of biliverdins increases with the stretching of the conformation. Biliverdin IX gamma (all-syn) has a pKa = 3.6; 5,10,15-syn,syn,anti-biliverdin has a pKa = 3.7; 5,10,15-syn,anti,syn-biliverdin has a pKa = 6.1; 5,10,15-syn,anti,anti-biliverdin has a pKa = 6.4; and 5,10,15-all-anti-biliverdin has a pKa = 7.9. The increase in basicity with progressive stretching of conformations closely parallels the increase in the reduction rates by BvR. A biliverdin constrained by a four carbon chain to a helical conformation and which is a very weak base (pKa = 0.4) is not reduced by BvR. Nucleophilic additions of 2-mercaptoethanol at the C10 in biliverdins closely parallel their basicities, as can be expected if the formation of a positive mesomeric species at C10 is linked to the basicity (i.e., the ease of protonation) of the N23 on the pyrrolenine ring.
S Bari; R B Frydman; C Grosman; B Frydman
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Biochemical and biophysical research communications     Volume:  188     ISSN:  0006-291X     ISO Abbreviation:  Biochem. Biophys. Res. Commun.     Publication Date:  1992 Oct 
Date Detail:
Created Date:  1992-11-19     Completed Date:  1992-11-19     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0372516     Medline TA:  Biochem Biophys Res Commun     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  48-56     Citation Subset:  IM    
Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Argentina.
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MeSH Terms
Biliverdine / analogs & derivatives*,  chemistry*,  metabolism
Molecular Conformation
Molecular Structure
Oxidoreductases / metabolism*
Oxidoreductases Acting on CH-CH Group Donors*
Structure-Activity Relationship
Reg. No./Substance:
114-25-0/Biliverdine; EC 1.-/Oxidoreductases; EC 1.3.-/Oxidoreductases Acting on CH-CH Group Donors; EC reductase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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