Display Settings:

Format

Send to:

Choose Destination
We are sorry, but NCBI web applications do not support your browser and may not function properly. More information
J Bacteriol. 2003 Jan;185(1):126-34.

Metal ion dependence of recombinant Escherichia coli allantoinase.

Author information

  • 1Department of Microbiology & Molecular Genetics, Michigan State University, East Lansing, MI 48824-4320, USA.

Abstract

Allantoinase is a suspected dinuclear metalloenzyme that catalyzes the hydrolytic cleavage of the five-member ring of allantoin (5-ureidohydantoin) to form allantoic acid. Recombinant Escherichia coli allantoinase purified from overproducing cultures amended with 2.5 mM zinc, 1 mM cobalt, or 1 mM nickel ions was found to possess approximately 1.4 Zn, 0.0 Co, 0.0 Ni, and 0.4 Fe; 0.1 Zn, 1.0 Co, 0.0 Ni, and 0.2 Fe; and 0.0 Zn, 0.0 Co, 0.6 Ni, and 0.1 Fe per subunit, respectively, whereas protein obtained from nonamended cultures contains near stoichiometric levels of iron. We conclude that allantoinase is incompletely activated in the recombinant cells, perhaps due to an insufficiency of a needed accessory protein. Enzyme isolated from nonsupplemented cultures possesses very low activity (k(cat) = 34.7 min(-1)) compared to the zinc-, cobalt-, and nickel-containing forms of allantoinase (k(cat) values of 5,000 and 28,200 min(-1) and 200 min(-1), respectively). These rates and corresponding K(m) values (17.0, 19.5, and 80 mM, respectively) are significantly greater than those that have been reported previously. Absorbance spectroscopy of the cobalt species reveals a band centered at 570 nm consistent with five-coordinate geometry. Dithiothreitol is a competitive inhibitor of the enzyme, with significant K(i) differences for the zinc and cobalt species (237 and 795 micro M, respectively). Circular dichroism spectroscopy revealed that the zinc enzyme utilizes only the S isomer of allantoin, whereas the cobalt allantoinase prefers the S isomer, but also hydrolyzes the R isomer at about 1/10 the rate. This is the first report for metal content of allantoinase from any source.

PMID:
12486048
[PubMed - indexed for MEDLINE]
PMCID:
PMC141845
Free PMC Article

Images from this publication.See all images (6)Free text

FIG. 1.
FIG. 2.
FIG. 3.
FIG. 4.
FIG. 5.
FIG. 6.
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Write to the Help Desk