Stone1996 - activation of soluble guanylate cyclase by nitric oxide

Stone1996 - activation of soluble guanylate
cyclase by nitric oxide
This features the two step binding of
NO to soluble Guanylyl Cyclase as proposed by
Stone
JR, Marletta MA. Biochemistry (1996) 35(4):1093-9 . There is a
fast step binding scheme and a slow step binding scheme. The
difference lies in the binding of a NO to a non-heme site on sGC,
which may not necessarily be the same site of binding during the
initial binding. The rates have been directly used models.

This model is described in the article:

Spectral and kinetic studies
on the activation of soluble guanylate cyclase by nitric
oxide.

Stone JR, Marletta MA.
Biochemistry 1996 Jan; 35(4):
1093-1099
Abstract:

The soluble form of guanylate cyclase (sGC) is the only
definitive receptor for the signaling agent nitric oxide (.NO).
The enzyme is a heterodimer of homologous subunits in which
each subunit binds 1 equiv of 5-coordinate high-spin heme. .NO
increases the Vmax of sGC up to 400-fold and has previously
been shown to bind to the heme to form a 5-coordinate complex.
Using stopped-flow spectrophotometry, it is demonstrated that
the binding of .NO to the heme of sGC is a complex process. .NO
first binds to the heme to form a 6-coordinate nitrosyl
complex, which then converts to a 5-coordinate nitrosyl complex
through one of two ways. For 28 +/- 4% of the heme, the
6-coordinate nitrosyl complex rapidly (approximately 20 s-1)
converts to the 5-coordinate complex. For the remaining 72 +/-
4% of the heme, the conversion of the 6-coordinate nitrosyl
complex to a 5-coordinate nitrosyl complex is slow (0.1-1.0
s-1) and is dependent upon the interaction of .NO with an
unidentified non-heme site on the protein. The heme (200 nM)
was completely converted to the 5-coordinate state with as
little as 500 nM .NO, and the equilibrium dissociation constant
of .NO for activating the enzyme was determined to be < or =
250 nM. Gel-filtration analysis indicates that the binding of
.NO to the heme has no effect on the native molecular mass of
the protein. Correlation of electronic absorption spectra with
activity measurements indicates that the 5-coordinate nitrosyl
form of the enzyme is activated relative to the resting
5-coordinate ferrous form of the enzyme.

This model is hosted on
BioModels Database
and identified by:
BIOMD0000000198.
To cite BioModels Database, please use:
BioModels Database:
An enhanced, curated and annotated resource for published
quantitative kinetic models.

To the extent possible under law, all copyright and related or
neighbouring rights to this encoded model have been dedicated to
the public domain worldwide. Please refer to
CC0
Public Domain Dedication for more information.