From owner-metabolic-reg@net.bio.net Sun Apr 25 23:00:00 1999 Path: biosci!news.stanford.edu!newsfeed.stanford.edu!news-feed.inet.tele.dk!bofh.vszbr.cz!remarQ-uK!remarQ.com!supernews.com!diablo.theplanet.net!diablo.dera.gov.uk!server1.netnews.ja.net!pegasus.csx.cam.ac.uk!hgmp.mrc.ac.uk!biosci From: daf@brookes.ac.uk (David Fell) Newsgroups: bionet.metabolic-reg Subject: Re: rate limiting vs rate determining Date: 26 Apr 1999 17:39:50 +0100 Organization: MRC Human Genome Mapping Project Resource Centre Lines: 34 Message-ID: <3.0.1.32.19990426174058.006beaf0@csmail.brookes.ac.uk> References: <9942616110.~INN-AOCa00156.bionet-news@dl.ac.uk> NNTP-Posting-Host: mercury.hgmp.mrc.ac.uk Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" X-Trace: niobium.hgmp.mrc.ac.uk 925144790 27947 193.62.192.80 (26 Apr 1999 16:39:50 GMT) X-Complaints-To: news@hgmp.mrc.ac.uk NNTP-Posting-Date: 26 Apr 1999 16:39:50 GMT X-Received: from mserv1.dl.ac.uk (root@mserv1.dl.ac.uk [148.79.160.65]) by hgmp.mrc.ac.uk (8.9.3/8.9.3) with ESMTP id RAA25554 for ; Mon, 26 Apr 1999 17:39:47 +0100 (BST) X-Received: from brookes.ac.uk (csmail.brookes.ac.uk [161.73.1.1]) by mserv1.dl.ac.uk with ESMTP id RAA09263 (8.8.8/5.4[ref postmaster@dl.ac.uk] for dl.ac.uk from daf@brookes.ac.uk); Mon, 26 Apr 1999 17:39:46 +0100 (BST) X-Precedence: first-class X-Received: from bms-daf.brookes.ac.uk by brookes.ac.uk (8.8.7/) id RAA29787; Mon, 26 Apr 1999 17:39:45 +0100 (BST) X-Sender: e0193069@csmail.brookes.ac.uk X-Mailer: Windows Eudora Light Version 3.0.1 (32) X-To: btk-mca@dl.ac.uk X-In-Reply-To: <9942616110.~INN-AOCa00156.bionet-news@dl.ac.uk> Guy Brown wrote: > >Note that this excellent paper of Ray's still accepts the >concept that there will always be a rate-limiting step, >and that the concept is coherent, rather than control >being shared and the distribution of control varying >with conditions. > >In our original paper on rate limitation within enzymes >we defined rate limitation in terms of Metabolic Control >Analysis, and used this to analyse rate-limitation within >three enzymes where all the rate constants had been >measured, etc ...... I'm glad Guy has responded with this note about his paper. I'd been meaning to post a reply referring to his work because I agree that he's quite clearly shown that distribution of control, and redistribution according to conditions, apply as much to enzyme mechanisms as they do to metabolic pathways. Hence however you redefine 'rate-determining', you can't get away from the fact that you can't uniquely identify such a step in an enzyme mechanism that will be valid under all circumstances. David ========================================================= David Fell, School of Biological & Molecular Sciences, Oxford Brookes University, Oxford OX3 0BP, UK Tel. +44 (0)1865 483247 FAX +44 (0)1865 484017 http://www.brookes.ac.uk/bms/research/molcell/fell/mca_rg/mca_home.html "Understanding the Control of Metabolism" now also available from Princeton University Press: http://pup.princeton.edu/titles/6512.html --- .