scholarly journals Determination of Pre-Steady-State Rate Constants on the Escherichia coli Pyruvate Dehydrogenase Complex Reveals That Loop Movement Controls the Rate-Limiting Step

2012 ◽  
Vol 134 (45) ◽  
pp. 18644-18655 ◽  
Author(s):  
Anand Balakrishnan ◽  
Natalia S. Nemeria ◽  
Sumit Chakraborty ◽  
Lazaros Kakalis ◽  
Frank Jordan
Keyword(s):  
Escherichia Coli ◽  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Complex ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Steady State Rate ◽  
State Rate ◽  
Rate Limiting ◽  
Dehydrogenase Complex

scholarly journals Control analysis applied to single enzymes: can an isolated enzyme have a unique rate-limiting step?

1993 ◽  
Vol 294 (1) ◽  
pp. 87-94 ◽  
Author(s):  
G C Brown ◽  
C E Cooper
Keyword(s):  
Rate Constants ◽  
General Assumption ◽  
Control Analysis ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Steady State Rate ◽  
Carbamate Kinase ◽  
State Rate ◽  
Rate Limiting ◽  
Control Coefficients

Control analysis is used to analyse and quantify the concept of a rate-limiting step within an enzyme. The extent to which each rate constant within the enzyme limits the steady-state rate of the enzyme and the levels of enzyme intermediate species are quantified as flux and concentration control coefficients. These coefficients are additive and obey summation theorems. The control coefficients of triose phosphate isomerase, carbamate kinase and lactate dehydrogenase are calculated from literature values of the rate constants. It is shown that, contrary to previous assumption, these enzymes do not have a unique rate-limiting step, but rather flux control is shared by several rate constants and varies with substrate, product and effector concentrations, and with the direction of the reaction. Thus the general assumption that an enzyme will have a unique rate-limiting step is unjustified.

scholarly journals Characterization of a Baculovirus-Encoded RNA 5′-Triphosphatase

1998 ◽  
Vol 72 (9) ◽  
pp. 7057-7063 ◽  
Author(s):  
Christian H. Gross ◽  
Stewart Shuman
Keyword(s):  
Steady State ◽  
Product Formation ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Mrna Capping ◽  
Steady State Rate ◽  
Rna Triphosphatase ◽  
State Rate ◽  
Nuclear Polyhedrosis ◽  
Rate Limiting

ABSTRACT Autographa californica nuclear polyhedrosis virus (AcNPV) encodes a 168-amino-acid polypeptide that contains the signature motif of the superfamily of protein phosphatases that act via a covalent cysteinyl phosphate intermediate. The sequence of the AcNPV phosphatase is similar to that of the RNA triphosphatase domain of the metazoan cellular mRNA capping enzyme. Here, we show that the purified recombinant AcNPV protein is an RNA 5′-triphosphatase that hydrolyzes the γ-phosphate of triphosphate-terminated poly(A); it also hydrolyzes ATP to ADP and GTP to GDP. The phosphatase sediments as two discrete components in a glycerol gradient: a 9.5S oligomer and 2.5S putative monomer. The 2.5S form of the enzyme releases 32Pi from 1 μM γ-32P-labeled triphosphate-terminated poly(A) with a turnover number of 52 min−1 and converts ATP to ADP with V max of 8 min−1and Km of 25 μM ATP. The 9.5S oligomeric form of the enzyme displays an initial pre-steady-state burst of ADP and Pi formation, which is proportional to and stoichiometric with the enzyme, followed by a slower steady-state rate of product formation (approximately 1/10 of the steady-state rate of the 2.5S enzyme). We surmise that the oligomeric enzyme is subject to a rate-limiting step other than reaction chemistry and that this step is either distinct from or slower than the rate-limiting step for the 2.5S enzyme. Replacing the presumptive active site nucleophile Cys-119 by alanine abrogates RNA triphosphatase and ATPase activity. Our findings raise the possibility that baculoviruses encode enzymes that cap the 5′ ends of viral transcripts synthesized at late times postinfection by a virus-encoded RNA polymerase.

scholarly journals Escherichia coli Peptidase A, B, or N Can Process Translation Inhibitor Microcin C

2008 ◽  
Vol 190 (7) ◽  
pp. 2607-2610 ◽  
Author(s):  
Teymur Kazakov ◽  
Gaston H. Vondenhoff ◽  
Kirill A. Datsenko ◽  
Maria Novikova ◽  
Anastasia Metlitskaya ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Cell Growth ◽  
Trna Synthetase ◽  
Methionine Residue ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Translation Inhibitor ◽  
Rate Limiting ◽  
Broad Specificity

ABSTRACT The heptapeptide-nucleotide microcin C (McC) targets aspartyl-tRNA synthetase. Upon its entry into a susceptible cell, McC is processed to release a nonhydrolyzable aspartyl-adenylate that inhibits aspartyl-tRNA synthetase, leading to the cessation of translation and cell growth. Here, we surveyed Escherichia coli cells with singly, doubly, and triply disrupted broad-specificity peptidase genes to show that any of three nonspecific oligopeptidases (PepA, PepB, or PepN) can effectively process McC. We also show that the rate-limiting step of McC processing in vitro is deformylation of the first methionine residue of McC.

Sign in / Sign up

Export Citation Format

Share Document