Give examples of the interrelationships between the structure and function of enzymes

An enzyme is a protein and also partially DNA.

The function of an enzyme depends on its structure, mainly because its structure determines the affinity for the binding of different substrates, as well as the high degree of coherence of the reaction sites for substrate processing, etc.

Its main biological functions are:

1) Catalytic and regulatory ability Some proteins are enzymes that catalyze the metabolic reactions of substances in living organisms. Some proteins are hormones that have certain regulatory functions, such as insulin regulating glucose metabolism, and signal transduction in vivo is often mediated by certain proteins.

2) Transport function Some proteins have the function of transporting, such as hemoglobin is a tool for transporting oxygen and carbon dioxide, and serum albumin can transport free fatty acids and bilirubin.

3) Contraction or locomotor function Certain proteins give cells and organs the ability to contract, allowing them to change shape or move. For example, skeletal muscle contraction depends on actin and myobulb egg, white.

4) Defensive functions such as immunoglobulins, which can resist foreign harmful substances and protect the body.

5) Nutritional and storage functions such as ferritin can store iron.

6) Structural proteins Many proteins play a supporting role in giving strength and protection to biological structures, such as ligaments, which contain elastin, which have two-way tensile strength.

7) Other functions such as viruses and bacteriophages are nuclear proteins, and viruses can cause disease.

2. Molecular composition of protein (1) Elemental composition The main elements that make up protein molecules are carbon, hydrogen, oxygen, nitrogen, and sulfur. Some also contain small amounts of phosphorus or metallic elements. The nitrogen content of various proteins is very similar, averaging 16, and protein is the main nitrogen content in the body, so the approximate content of protein can be deduced from the nitrogen content of biological samples.

The main component of most enzymes is protein, which is made up of amino acids. There is a structure called a polypeptide chain between them.

It is mainly used to catalyze different substances. For example, pepsin is found in the human stomach to assist digestion.

It is a highly efficient catalyst, much more efficient than many inorganic catalysts.

Enzymes are proteins, and they are found in many internal organs, and their role is to act as catalysts, such as salivary amylase in the mouth, which helps digest food.

The binding enzyme consists of two parts:

1. The protein part is called the enzyme protein;

Function: Determines the specificity of the reaction.

2. The non-protein part (usually called the mu shed as a cofactor) is mostly small molecule organic compounds or metal ions;

Function: Determines the type and nature of the reaction.

Enzymes are macromolecular biocatalysts with a close relationship between their structure and function. Regulation of enzyme activity can be achieved by changing the macromolecular structure of enzymes. For example, insulin in the human body is a protein that stimulates glucose absorption and utilization, while also regulating glucose metabolism in the liver and muscles.

By binding to the insulin receptor, insulin activates tyrosine kinases, which in turn phosphorylates enzyme proteins, thereby regulating their activity. This enzyme regulation is achieved by changing the molecular structure of insulin, i.e., the difference in the molecular structure of insulin can lead to changes in the binding capacity of insulin to receptors and enzyme activity. In addition, there are many other enzymes, such as DNA polymerase, acid phosphatase, etc., which are regulated by the regulation of molecular structure.

Therefore, the molecular structure of enzymes is closely related to their functions, and changes in molecular structure can cause changes in enzyme functions, so as to achieve the regulation of enzyme activity.

Journal of Shaanxi Normal University (Natural Science Edition), No.01, 2003.

Supramolecular structure and function of F 1F 0-ATPase.

Sun Runguang Abstract]:The study of the structure and function of F1F0 ATPase by X-ray diffraction crystallography, fluorescence labeling microscopy, negative chromosome electron microscopy and monoclonal antibody technology has found that in Escherichia coli, chloroplast and bovine heart mitochondria, the F1F0 ATPase complex is composed of 16 different subunits, respectively. All F1F0 ATPases have a similar structure, with the globular F1 and F0 connected by a central shaft and a peripheral stalk.

Among them, the central transient axis is composed of and subunit, and the peripheral stalk is composed of b2(, and δ subunits. During the catalysis of the enzyme, the 3-3 subunit interacts with the C subunit ring on the membrane through the subunit, driving the central spindle rotation of the ATP synthase. F1F0 ATPase catalyzes the formation of ATP (adenosine triphosphate) from ADP (adenosine diphosphate) and PI (inorganic phosphate) using the source energy of the finch seepage source of the electrochemical proton gradient

The binding enzyme consists of two parts:

1. The protein part is called the enzyme protein;

Function: Determines the specificity of the reaction.

2. The non-protein part (commonly known as a cofactor) is mostly small molecule organic compounds or metal ions;

Function: Determines the type and nature of the reaction.

It is also called a two-component enzyme. The binding enzyme consists of two parts:

The protein part, called the enzyme protein, determines the specificity of the reaction;

The non-protein fraction (often referred to as a cofactor), mostly small organic compounds or metal ions, determines the type and nature of the reaction.

There are many ways to adjust the activity of enzymes by changing the structure of enzymes in living organisms.

Answer: (1) Allosteric regulation: The conformational change occurs after the oligomerase molecule is reversibly non-covalently bound to the substrate or non-substrate effector, which then changes the enzyme activity state, so that the enzyme activity is regulated.

For example, after the partial catalytic peptide chain of aspartate transcarbamylase binds to the substrate, the overall conformation of the enzyme is changed, and the affinity of other catalytic peptide chains and the substrate is improved.

2) Activation of zymogen: under the specific action of proteolytic enzymes, the inactive zymogen leads to a change in its conformation through the change of its primary structure, forming the active site of the enzyme and becoming an active enzyme, which is an irreversible regulation method to make the enzyme active. For example, in the small intestine, under the action of trypsin, the specific peptide bond of the non-catalytically active chymotrypsinogen is broken, and a complete peptide chain is hydrolyzed into a three-segment peptide chain, and the conformational change occurs, forming the active site, and producing proteolytic enzyme activity.

3) Reversible covalent modification: other enzymes (such as kinases, phosphatases, etc.) catalyze covalent regulatory enzymes to covalently modify or remove modified groups, so that their structure changes, so as to transform between active and inactive forms to regulate the activity of enzymes. For example, glycogen phosphorylase can exist in two forms, one is the high-activity glycogen phosphorylase A where Ser14 is phosphorylated, and the other is the non-phosphorylated, low-activity glycogen phosphorylase B, which is phosphorylated by the phosphorylase kinase, and the Ser14 of glycogen phosphorylase B is phosphorylated to form the high-activity glycogen phosphorylase A; Under the catalysis of phosphorylase phosphatase, Ser14-PO32- of glycogen phosphorylase A is dephosphorylated to form low-activity glycogen phosphorylase B.

4) The regulation of oligomerase activity can be carried out by changing its quaternary structure, which includes both dissociation of inactive oligomers and catalytic activity of some subunits, as well as polymerization of inactive monomers to form catalytically active oligomers. An example of the former is protein kinase A, which consists of 2 regulatory subunits and 2 catalytic subunits, which is an oligomerase with no enzymatic activity, and the binding of the intracellular messenger camp to the regulatory subunit can cause the oligomerase to dissociate into a regulatory subunit complex and two catalytic subunits, at which point the free catalytic subunit can acquire enzymatic activity. An example of the latter is the epidermal growth factor receptor, which normally exists as an inactive monomer on the cell membrane, and when the epidermal growth factor as a messenger binds to the extracellular part of the receptor, the two monomers combine to form a dimer, which allows the enzyme to be activated.