Please respond to Achim. Ron Blue
---------- Forwarded message ----------
Date: Thu, 06 Jun 1996 14:46:43 -0500
From: Achim Recktenwald <achim at ibex.ca>
To: biophys at net.bio.net
Subject: Why is solubility phe > tyr ?
I have a question concerning the solubilities of the amino acids phenylalan=
ine and=20
tyrosine.
I had posted this message already a few weeks ago, but received no answer, =
therefore, I am=20
trying again, and to more Newsgroups.
I am working with an enzyme that accepts phenylalanine (phe) and tyrosine (=
tyr) as=20
substrate.
When I prepared the first time stock solutions I was surprised to notice th=
at phe is=20
soluble in water at pH 7 +/- 1 pH to approx. 180 mM, while with tyr I can p=
repare at the=20
same conditions only a 10 mM solution.
Tyr differs from phe only in an additional hydroxyl-group.
I had always assumed an increase in polarity would also make a substance mo=
re water=20
soluble.
Can anybody explain to me, why the p-OH group in tyrosine has such a strong=
effect on the=20
solubility of the amino acid, nin effect decreasing it almost to 1/20 of ph=
e.
Is this only valid for the free enzyme, or would this also be the case for =
the amino acid=20
side-chains in proteins? Does this mean, phe-side-chains have a more hydro=
philic=20
character than tyr=B9s in proteins?
Achim
=01=01=01=01
