What is the substrate for aconitase?
What is the substrate for aconitase?
The enzyme aconitase is a key player in the central pathway of energy production. As part of the citric acid cycle, it converts citrate into isocitrate. The animation shows histidine acting as an acid protonates the hydroxyl on the substrate, allowing it to leave as a water molecule.
What is the cofactor of aconitase?
The (4Fe-4S) cofactor is held in place by three sulfur atoms belonging to the cysteins-385, -448, and -451 which are bound to three of the four cluster iron atoms. Substrate-free aconitase contains a [4Fe-4S]2+ cluster with hydroxyl bound to one of the Fe.
What happens if aconitase is inhibited?
CAA by reduction of cellular glutathione can cause oxidative stress. Inhibition of mitochondrial aconitase causes hypoglycemia.
What enzyme class is aconitase?
Enzyme
Aconitase/Classification
Is aconitase a Dehydratase?
Structure of aconitase. Aconitase (aconitate hydratase; EC 4.2. 1.3) is an enzyme that catalyses the stereo-specific isomerization of citrate to isocitrate via cis-aconitate in the tricarboxylic acid cycle, a non-redox-active process.
Is aconitase reversible?
Aconitase (aconitate hydratase; citrate hydrolyase; EC 4.2. 1.3) catalyzes the reversible stereo-specific isomerization of citrate to isocitrate via cis-aconitate as an intermediate in a non-redox-active manner (Fig. 1). Aconitase belongs to the family of iron–sulfur-containing dehydratases.
Why is fluoroacetate toxic?
Fluoroacetate (FA; CH2FCOOR) is highly toxic towards humans and other mammals through inhibition of the enzyme aconitase in the tricarboxylic acid cycle, caused by ‘lethal synthesis’ of an isomer of fluorocitrate (FC). FA is found in a range of plant species and their ingestion can cause the death of ruminant animals.
Is Fumarase an iron sulfur protein?
Iron-sulfur clusters are the traces of biological evolution in the early anaerobic earth. Dehydratases that contain [4Fe–4S] clusters, such as fumarase, aconitase and isopropylmalate isomerase (IPMI), are such proteins [[12], [13], [14], [15]].
Which reaction is catalyzed by lyase?
In biochemistry, a lyase is an enzyme that catalyzes the breaking (an elimination reaction) of various chemical bonds by means other than hydrolysis (a substitution reaction) and oxidation, often forming a new double bond or a new ring structure. The reverse reaction is also possible (called a Michael reaction).
Is aconitase a isomerase or lyase?
The iron-responsive element-binding protein (IRE-BP) and 3-isopropylmalate dehydratase (α-isopropylmalate isomerase; EC 4.2. 1.33), an enzyme catalysing the second step in the biosynthesis of leucine, are known aconitase homologues.
What is the function of cytosolic aconitase?
Cytosolic aconitase links iron metabolism, unfolding and proteolytic degradation of proteins with ROS metabolism. Oxidation of aconitase by ROS/RNS results in loss of labile iron, inactivating the enzyme and switching the function to regulation of iron metabolism as iron regulatory protein 1 (IRP1).
How is aconitase inhibited by the citric acid cycle?
Aconitase is inhibited by fluoroacetate, therefore fluoroacetate is poisonous. Fluoroacetate, in the citric acid cycle,can innocently enter as fluorocitrate. However, aconitase cannot bind this substrate and thus the citric acid cycle is halted. The iron sulfur cluster is highly sensitive to oxidation by superoxide.
Why is cis aconitate released in the isocitrate mode?
One theory is that, in the rate-limiting step of the mechanism, the cis -aconitate is released from the enzyme, then reattached in the isocitrate mode to complete the reaction. This rate-limiting step ensures that the right stereochemistry, specifically (2R,3S), is formed in the final product.
Which is an enzyme that catalyses the stereo specific isomerization of citrate?
Aconitase (aconitate hydratase; EC 4.2.1.3) is an enzyme that catalyses the stereo-specific isomerization of citrate to isocitrate via cis – aconitate in the tricarboxylic acid cycle, a non- redox -active process.
How is the conversion of citrate to isocitrate measured?
Citrate-to-isocitrate conversion was measured by coupling to yeast Idp (GE Healthcare, Piscataway, NJ) and monitoring NADPH production in 0.1 M Tris-Cl (pH 8.0) containing 1.0 mM each of MgCl 2, NADP +, and disodium citrate, and 0.4 unit of Idp ( 19 ).