Subject: Summary of metal-bound water pKa data

From: [email-masked] (Mark Murcko)
Date: Thu, 7 Sep 1995 23:01:50 -0500 (EDT)

Here is a summary of the responses to my recent question about 
the pKa of waters bound to metals in proteins.  Thanks to all
who contributed!

/ Mark ([email-masked])

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From: [email-masked] (Lars Hemmingsen)

concerning your question about pKa's of metalbound water in proteins:

For the zinc enzyme horse liver alcohol dehydrogenase I can give you the 
following values (NAD+/NADH is a coenzyme, which binds close to the metal)

LADH-H2O: pKa=9.2,   LADH-NAD+-H2O: pKa=7.6, LADH-NADH-H2O: 11.2
(Kvassmann and Pettersson 1980 Eur. J. Biochem., 103, 565-575 
and Kvassmann and Pettersson 1987 Eur. J. Biochem., 166, 167-172.

and for the same enzyme with the zinc ion exchanged with cadmium:
LADH-H2O: pKa=11.0, LADH-NAD+-H2O: pKa=9.2, LADH-NADH-H2O: Not measured
(Hemmingsen et al. 1995 Biochemistry, 35, 7145-7153.

Furthermore pKa's have been measured, by the group of professor Michael
Zeppezauer in Saarbrucken, for the same enzyme with the zinc ion
exchanged with cobalt (the references and numbers are in the Biochemistry
reference). If you want more pKa-values I would suggest that you contact
the poeple in Saarbrucken, Germany (fax: +49 681 302 2097)

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