{"id":7323,"date":"2024-09-12T11:27:09","date_gmt":"2024-09-12T11:27:09","guid":{"rendered":"https:\/\/longchangchemical.com\/?p=7323"},"modified":"2026-04-28T10:42:35","modified_gmt":"2026-04-28T10:42:35","slug":"what-is-the-structure-and-function-of-enzymes","status":"publish","type":"post","link":"https:\/\/longchangchemical.com\/zh\/what-is-the-structure-and-function-of-enzymes\/","title":{"rendered":"\u9176\u7684\u7ed3\u6784\u548c\u529f\u80fd\u662f\u4ec0\u4e48\uff1f"},"content":{"rendered":"

Composition of enzymes<\/p>\n

Simple enzymes: enzymes composed only of amino acid residues.<\/p>\n

Bound enzymes: composed of enzyme proteins and non-protein cofactors<\/p>\n

Enzyme protein: determines the specificity of the reaction;<\/p>\n

Cofactors: determine the type and nature of the reaction; can be metal ions or small organic compounds.<\/p>\n

 <\/p>\n

Cofactors<\/p>\n

Cofactor: loosely bound to enzyme protein, can be removed by dialysis or ultrafiltration.<\/p>\n

Cofactor: tightly bound to enzyme protein, cannot be removed by dialysis or ultrafiltration.<\/p>\n

The complex formed by the combination of enzyme protein and cofactor is called holoenzyme, and only holoenzyme has catalytic effect.<\/p>\n

 <\/p>\n

The active centre of enzyme<\/p>\n

\u2460Enzyme necessary groups: necessary for the enzyme to play the activity of the group<\/p>\n

\u2461 the active centre of the enzyme: in the primary structure is very far apart, but in the spatial structure of some of the R groups close to each other to form a special region, the region can specifically bind the substrate and catalyze the substrate to undergo chemical changes.<\/p>\n

The active centre must groups are divided into:<\/p>\n

Binding groups: involved in enzyme-substrate binding<\/p>\n

Catalytic groups: catalyse the transformation of substrates into products.<\/p>\n

Required groups outside the active centre: there must be a required group within the active centre, but the required group may not always be in the active centre. The mandatory group outside the active centre serves to stabilise the active centre.<\/p>\n

 <\/p>\n

Difference between enzyme and general catalyst<\/p>\n

\u2460 high efficiency: the catalytic effect of the enzyme can increase the reaction rate of 10^6 to 10^12 times, before and after the reaction of the enzyme itself does not change, high efficiency is to reduce the activation energy of the reaction<\/p>\n

\u2461Specificity (selectivity for substrate)<\/p>\n

\u2160 absolute specificity: the enzyme is very strict on the substrate requirements, only a specific substrate;<\/p>\n

\u2161 relative specificity: the object of action is not a substrate, but a class of compounds or chemical bonds;<\/p>\n

\u2162 stereoisomer specificity: D-, L-, cis-trans<\/p>\n

\u2462 Enzyme activity instability: proteins are easily denatured and inactivated<\/p>\n

\u2463Enzyme activity can be regulated and controlled: \u2160 allosteric regulation; \u2161 feedback regulation; \u2162 valence-dependent modification regulation; \u2163 zymogen activation and hormone control<\/p>\n

 <\/p>\n

Doctrine of induced fit<\/p>\n

The enzyme surface does not have a fixed shape that is complementary to the substrate, but only forms a complementary shape due to the induction of the substrate.<\/p>\n

 <\/p>\n

Factors affecting the enzymatic reaction<\/p>\n

(1) substrate concentration; (2) inhibitor; (3) enzyme concentration; (4) temperature; (5) pH; (6) activator.<\/p>\n

 <\/p>\n

The effect of substrate concentration on the rate of enzymatic reaction:<\/p>\n

Intermediate product doctrine: when enzyme catalysis, the enzyme active centre first combines with the enzyme substrate to form a complex of an enzyme and a substrate, which then decomposes to release the enzyme and releases the products<\/p>\n

Mie’s equation: V=Vmax\u00d7[S]\/(Km+[S])<\/p>\n

(1) When the substrate concentration is very large ([S]\u226510\u00d7Km), the enzyme is saturated with the substrate, and the reaction rate reaches the maximum.<\/p>\n

(2) When the reaction velocity V=1\/2Vmax, Km=[S].<\/p>\n

The significance of the kinetic parameter Km in Mie’s equation\u2605<\/p>\n

\u2460Km is numerically equal to the substrate concentration corresponding to half of the maximum reaction rate, i.e., when V=1\/2Vmax, Km=[S]<\/p>\n

\u2461Km unit: mol\/L<\/p>\n

\u2462 different enzymes have different Km values, which is an important characteristic physical constant of enzymes<\/p>\n

The same enzyme has different Km values for different substrates, and the substrate with the smallest Km is called the most suitable substrate.<\/p>\n

\u2464 Km indicates the degree of affinity between the enzyme and the substrate: the larger the Km value, the smaller the affinity and the lower the catalytic activity; the smaller the Km value, the larger the affinity and the higher the catalytic activity<\/p>\n

 <\/p>\n

The effect of inhibitors on the rate of enzymatic reaction<\/p>\n

(1) Irreversible inhibition<\/p>\n

Inhibitors and the active group of the enzyme activity centre or some of the groups in its site in the form of covalent binding, causing enzyme inactivation, physical methods can not be eliminated<\/p>\n

 <\/p>\n

(2) Reversible inhibition<\/p>\n

\u2160 Competitive inhibition<\/p>\n

a. The chemical structure of the inhibitor is similar to that of the substrate, which can competitively bind to the enzyme active centre with the substrate;<\/p>\n

b.When the inhibitor binds to the active centre, the substrate is excluded from the reaction centre, with the result that the enzymatic reaction is inhibited;<\/p>\n

c. Increasing the concentration of the substrate increases the ability of the substrate to compete (i.e., it can release the inhibition);<\/p>\n

d. the Km value rises and the Vmax remains constant<\/p>\n

 <\/p>\n

II Non-competitive inhibition<\/p>\n

Binding to a mandatory group other than the active centre<\/p>\n

Km value remains unchanged, Vmax decreases<\/p>\n

 <\/p>\n

\u2162 anticompetitive inhibition<\/p>\n

Binding to enzyme-substrate complex<\/p>\n

Km value decreases, Vmax decreases<\/p>\n

 <\/p>\n

Activation of zymogen<\/p>\n

\u2460Enzymogen: inactive enzyme precursor<\/p>\n

\u2461Activation: primary structure change, causing conformational change, formation or exposure of active centre<\/p>\n

 <\/p>\n

Enzyme activity regulation<\/p>\n

\u2460 covalent modification of enzymes (chemical modification regulation): an enzyme is modified by another enzyme, covalently attached to a chemical group, or covalent bond breaking, remove a chemical group, thereby regulating the activity of enzymes<\/p>\n

\u2461 allosteric regulation: some substances can be reversibly bound to the active centre of the corresponding enzyme molecule or a specific part of the molecule other than the active centre, so that the enzyme’s active centre conformation changes, resulting in functional changes<\/p>\n

 <\/p>\n

Isoenzyme<\/p>\n

\u2460 refers to the catalytic chemical reaction is the same, the enzyme protein molecular structure, physical and chemical properties and immunological properties of a group of different enzymes \u2461 this kind of enzyme exists in the same species of organisms or the same body of different tissues or even the same tissue or cells<\/p>\n

 <\/p>\n

Trypsin as an example of the relationship between protein structure and function<\/p>\n

Because trypsin is far apart in the primary structure, enterokinase cuts the N-terminal 6 peptide, so that its primary conformation changes, forming a special region, that is, the active centre of the enzyme, the region can specifically bind the substrate and catalyse the substrate to undergo a chemical change, playing a binding and catalytic function, explaining the change in the primary structure, causing a change in the conformation, the formation of the active centre, so that the tryptic protein from inactive to active.<\/p>\n

<\/p>\n

A practical sourcing checklist for enzyme, biotech, and food-ingredient topics<\/h2>\n

In enzyme and food-processing projects, the most useful decision frame is usually application fit plus process stability: which ingredient performs under the intended pH, temperature, time, and substrate conditions without creating a downstream quality or compliance problem.<\/p>\n