Biochem lecture 1

Chemical processes are fundamental to the vital activities of organisms.
Enzymes (E) are natural biocatalysts, essential in nearly all biochemical reactions.
Enzymes selectively transform reagents known as substrates (S), controlling all metabolic processes in the body.

Enzymes are critical components of the cell; their activity defines metabolism in living organisms.
They maintain homeostasis by regulating the rate and orientation of biochemical processes.
A deficiency or defect in an enzyme can result in severe consequences or diseases known as fermentopathies (enzymopathies).
Enzymes can serve as medicines (enzyme therapy) and diagnostic tests (enzyme diagnostics).
The unique set of enzymes within a cell is genetically programmed, contributing to cellular individuality.
Enzymes play roles in protective functions of the body.

Enzymes are not consumed in reactions; they exit unchanged after reactions.
They cannot initiate reactions violating thermodynamic laws but can accelerate reactions by lowering activation energy.
Enzymes do not alter the equilibrium of reversible reactions but facilitate the attainment of equilibrium.

Enzymes possess extremely high catalytic efficiency, often catalyzing transformations of 10^2 to 10^6 substrate molecules per minute.

Enzymes exhibit high specificity towards substrates and transformation pathways, categorized into:
- Absolute specificity: Active center fits only one substrate.
- Group specificity: Catalyzes reactions for a group of structurally similar substrates.
- Stereospecificity: Acts on specific stereoisomers.

Enzymes transform substrates through particular pathways determined by their active sites, even if the same substrate is involved in different reactions.

Enzymes can lose their native shape due to the disruption of weak bonds when exposed to denaturing agents, limiting their function to mild conditions.

Enzyme activity is influenced by substrate and product concentrations, cofactors, coenzymes, and allosteric modulators.

Enzymes are protein molecules containing an active center (AC) essential for biological function, characterized by amino acids that allow for specific substrate binding and transformation.
The active center is highly ordered and facilitates optimal catalysis, with significant spatial proximity of amino acids achieved through higher-order structures.

The binding site allows substrates to attach through non-covalent interactions, forming an enzyme-substrate complex (ES).
The catalytic site facilitates the chemical transformation of the substrate into products, which are subsequently released.
Important amino acids in the catalytic site include serine, histidine, and cysteine, defining the enzyme's classification.

Enzymes may have allosteric centers distinct from the active center, which can influence enzyme activity when low-molecular substances bind to them.
These modulators can act positively (increasing reaction rates) or negatively (decreasing reaction rates).

Simple enzymes consist solely of polypeptide chains, while complex enzymes contain non-protein components called cofactors.
The protein component is termed apoenzyme; the combination of an apoenzyme and a cofactor forms a holoenzyme.
- Prosthetic groups: Strongly bonded cofactors.
- Coenzymes: Weakly bonded cofactors.
- Cofactors can be either organic (e.g., FAD, NAD+) or inorganic (e.g., Mg2+, Zn2+).

Cofactors participate in catalysis, promote enzyme-substrate contact, or act as substrates in reactions.

Monomeric Enzymes: Single polypeptide chains representing the third level of protein structure (e.g., trypsin).
Oligomeric Enzymes: Consist of identical subunits forming a multimer (e.g., apoferritin).
Isoenzymes: Variants regulating the same reaction but differing in properties and structure.
Complex Enzymes: Different structure and function in oligomeric enzymes, separation of regulatory and catalytic functions.
Supramolecular Structures: Multienzyme complexes involved in several sequential reactions, e.g., metabolic pathways.
Enzyme Ensembles: Structural complexes in biological systems involving enzymes and other cellular components.

I Oxidoreductases: Catalyze redox reactions (dehydrogenases, oxidases).
II Transferases: Transfer functional groups between substrates (kinases, aminotransferases).
III Hydrolases: Catalyze hydrolysis reactions (esterases, proteases, lipases).
IV Lyases (Synthases): Catalyze non-hydrolytic cleavage to form double bonds (aldolases, decarboxylases).
V Isomerases: Facilitate the interconversion of isomers (isomerases, mutases).
VI Ligases (Synthetases): Join simpler molecules into complex ones using energy from ATP hydrolysis.
VII Translocases: Involved in movement across membranes.