ISSN:
1573-4927
Keywords:
Serratia marcescens
;
pyrimidine biosynthesis
;
enzyme aggregation
;
regulation
;
bacteria
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract Orotidine-5′-monophosphate pyrophosphorylase (OMPppase, E.C. 2.4.2.10) and orotidylate decarboxylase (OMPdecase, E.C. 4.1.1.23) were purified from Serratia marcescens HY. These enzymes required physical association for maximal catalytic activities and formed a fragile complex with dihydroorotase (DHOase, E.C. 3.5.2.3.). OMPppase reversibly lost 50% of its activity upon separation from DHOase. The kinetic characteristics of OMPppase were modified by this separation. In the presence of DHOase, the K ms for PRPP and orotate were stoichiometric: 2.3×10−6 m and 2.6×10−6 m, respectively. Following separation, the K ms were significantly different: 1.3 × 10−6 m for PRPP and 4.1×10−6 m for orotate. OMPppase and OMPdecase could be reversibly separated by acrylamide gel electrophoresis, but the separation was accompanied by a loss of catalytic efficiency for both enzymes. DHOase readily associated into multiple molecular forms and could not be purified. The DHOase-OMPppase-OMPdecase interactions demonstrate that a weakly aggregated, multifunctional enzyme complex participates in the biosynthesis of pyrimidine nucleotides in S. marcescens. This unique association of nonsequential biosynthetic enzymes may represent a larger complex which provides a channeling or regulatory unit.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00484560
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