summary URA3/OMP decarboxylase

Jaap Venema venema at EMBL-Heidelberg.DE
Tue Apr 4 03:50:43 EST 1995

This is a summary of the response I got to my question concerning
measurement of URA3 (OMP decarboxylase) enzymatic activity. Thank you very
much to those who have responded!

Eric Stephen (Eric_Stephen_at_NCOT203 at wrote:

The reference I am going to provide you must be one of the original methods
for determining OMP decarboxylase.  The reference is Beckwith, J.R., A.B.
Pardee, R. Austrian and F. Jacob (1962) Coordination of the synthesis of
the enzymes in the pyrimidine pathway of E. coli. J. Molec. Biol. 5:
618-634.  I have the assay conditions if you cannot access this paper.

Jeff Smiley (jas13 at wrote:

Lue et al. (Mol. Cell. Biol., 1987, Vol. 7, pp. 3446-51) used Ura3 to
monitor expression from a promoter.
Prabhakararao and Jones (Anal. Biochem., 1975, Vol. 69, pp. 451-67)
describe a C14 - CO2 displacement method.  Most other references on ODCase
from the M. E. Jones lab during the '80's describe this assay.

F. Iborra (iborra at wrote:

Do yeast extracts in Tris pH 8.3 in an 1 ml quartz cuvette
Add 900 ul Tris 0.1 M pH 8.3, 50-1OO ul extract and H2O =>1ml
Start the reaction at 30 degree by addition of 7.5 ul OMP 10 mM
Follow the decrease of absorbance at 285 nm
1 delta OD 285 = 72.464 nM decarboxylated
Ref: Beckwith et al. J. Mol Biol. (1962) 5:618-634

Jaap Venema

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