Pyruvate Metabolism and Enzyme Complexes

Flashcards based on lecture notes about Pyruvate and related biochemical processes.

Thiamine Pyrophosphate (TPP)

A derivative of vitamin B1 (thiamine) that plays a crucial role in enzymatic reactions, especially those involving decarboxylation. It is the active form of thiamine found in cells.

I Ylide form of Thiamine Pyrophosphate

The carbanion form of thiamine pyrophosphate, stabilized by its chemical structure, which can perform nucleophilic attacks on carbonyl carbons.

Decarboxylation

The removal of a carboxyl group (COOH) from a molecule, often facilitated by thiamine pyrophosphate, especially in the pyruvate dehydrogenase complex. This process releases carbon dioxide (CO2).

Mitochondrial Shuttle Systems

Mechanisms that transfer electrons from NADH produced during glycolysis into the mitochondrial matrix for use in the electron transport chain, allowing for ATP production under aerobic conditions.

Mitochondrial Membranes

The outer membrane is permeable due to porins, while the inner membrane is selectively permeable, requiring specific transport proteins to move molecules across, including pyruvate.

Coenzyme A (CoA)

A coenzyme containing pantothenic acid and a mercaptoethylamine moiety, essential for various biochemical reactions, including the formation of acetyl-CoA from pyruvate. It is shortened to CoA.

Anionic Bond of CoA

A high-energy bond in CoA whose hydrolysis releases a significant amount of energy, making it crucial for driving enzymatic reactions.

Multienzyme Complex

A group of enzymes physically associated to catalyze a series of sequential reactions, exemplified by the pyruvate dehydrogenase complex.

Electron Microscopy

A microscopy technique using electrons to visualize extremely small structures, such as large protein complexes like the pyruvate dehydrogenase complex.

Supramolecular Chemistry

The study of complex structures formed by the non-covalent assembly of multiple molecules, like lipid molecules in a membrane.

Allostery

The regulation of an enzyme by binding of an effector molecule at a site other than the enzyme's active site, inducing a conformational change or altering vibrational patterns that affect activity.

Tense and Relaxed Structures

Different conformational states of a protein, such as hemoglobin, with varying affinities for ligands like oxygen. These states may or may not involve significant conformational changes.

Intrinsically Disordered Proteins/Regions

Proteins or regions of proteins that lack a fixed or ordered three-dimensional structure, important for protein function and regulation.

Lipoamide

A cofactor involved in the transfer of acyl groups in biochemical reactions, such as in the pyruvate dehydrogenase complex, where it accepts a hydroxyethyl group.

Irreversible Reactions

Biochemical reactions, like decarboxylation coupled with dehydrogenation, that are highly exergonic and cannot be reversed under physiological conditions. Mammals cannot reverse the decarboxylation of pyruvate to synthesize glucose from CO2.

Alpha-Ketoglutarate Dehydrogenase Complex

An enzyme complex in the Krebs cycle similar in structure and function to the pyruvate dehydrogenase complex, catalyzing a similar decarboxylation and dehydrogenation reaction.