The two acireductone dioxygenase (ARD) isozymes from the methionine salvage pathway of Klebsiella oxytoca are the only known pair of naturally occurring metalloenzymes with distinct chemical and physical properties determined solely by the identity of the divalent transition metal ion (Fe2+ or Ni2+) in the active site. We now show that this dual chemistry can also occur in mammals. ARD from Mus musculus (MmARD) was studied to relate metal ion identity and three-dimensional structure to enzyme function. The iron-containing isozyme catalyzes the cleavage of 1,2-dihydroxy-3-keto-5-(thiomethyl)pent-1-ene (acireductone) by O2 to formate and the ketoacid precursor of methionine, the penultimate step in methionine salvage. The nickel bound form of ARD catalyzes an off-pathway reaction resulting in formate, carbon monoxide (CO) and 5-(thiomethyl) propionate. Recombinant MmARD was expressed and purified to obtain a homogeneous enzyme with a single transition metal ion bound. The Fe2+ bound protein, which shows about ten-fold higher activity than others, catalyzes on-pathway chemistry, whereas the Ni2+, Co2+ or Mn2+ forms exhibit off-pathway chemistry, as has been seen with ARD from Klebsiella. Thermal stability of the isozymes is strongly affected by metal ion identity, with Ni2+ bound MmARD being the most stable followed by Co2+ and Fe2+, and Mn2+-bound ARD being the least stable. Ni2+ and Co2+ bound MmARD were crystallized and the structures of the two proteins found to be similar. Enzyme-ligand complexes provide insight into substrate binding, metal coordination and catalytic mechanism.
This research output has an Altmetric Attention Score of 1. This is our high-level measure of the quality and quantity of online attention that it has received. This Attention Score, as well as the ranking and number of research outputs shown below, was calculated when the research output was last mentioned on 01 April 2016.
All research outputs
#24,596,978
of 34,189,811 outputs
Outputs from Biochemistry
#24,204
of 27,141 outputs
Outputs of similar age
#222,759
of 337,395 outputs
Outputs of similar age from Biochemistry
#78
of 148 outputs
Altmetric has tracked 34,189,811 research outputs across all sources so far. This one is in the 19th percentile – i.e., 19% of other outputs scored the same or lower than it.
So far Altmetric has tracked 27,141 research outputs from this source. They typically receive a little more attention than average, with a mean Attention Score of 5.0. This one is in the 7th percentile – i.e., 7% of its peers scored the same or lower than it.
Older research outputs will score higher simply because they've had more time to accumulate mentions. To account for age we can compare this Altmetric Attention Score to the 337,395 tracked outputs that were published within six weeks on either side of this one in any source. This one is in the 26th percentile – i.e., 26% of its contemporaries scored the same or lower than it.
We're also able to compare this research output to 148 others from the same source and published within six weeks on either side of this one. This one is in the 40th percentile – i.e., 40% of its contemporaries scored the same or lower than it.
