Km of restriction enzymes

Bill Jack jack at
Fri Sep 30 16:36:56 EST 1994

EcoRI has been reported to have Kms between 0.4 and 8 nM (EcoRI site
concentration), depending on the substrate used and the reaction
conditions. Turnover numbers are in the range 2-6 double strand cleavages
per dimer per minute. PaeR7I was recently reported to have a Km in the
range of 75 nM for 14-18-mer duplex oligonucleotides, with a kcat of about
20 per minute. EcoRV has been reported to have a Km of 0.5 nM with a kcat
of 1 per minute. TaqI is reported to have a Km of 53 nM with a kcat of 1.3
per minute.

If you need more information, or references, please contact me.

Bill Jack
jack at

In article <367cou$5v2 at>, mcdonald at (John H
McDonald) wrote:

> Does anyone know the Km for DNA of a "typical" restriction enzyme (or of
> AccI in particular)?  I'd like to digest a rather small amount of DNA, and
> I'm wondering if I need to add some other, generic DNA in order for the
> enzyme to work.  I'm hoping to digest one of two alleles in a heterozygous
> individual, then PCR amplify the uncut allele. 
> John H. McDonald
> Department of Biology
> University of Delaware

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