Conjugated Enzymes

Enzymes are biological catalysts that help living organisms speed up chemical reactions. Enzymes can only function in specified pH, pressure, and temperature conditions. Each chemical response in the body, they are highly specific and effective. They also reduce the activation energy necessary to start the reaction, resulting in a faster response. Enzymes do not alter during chemical reactions and can thus be utilised multiple times. Simple enzymes like trypsin, pepsin, and urease do not require cofactors, however other enzymes do require small non-protein molecules called cofactors, and these enzymes are referred to as conjugate enzymes. Cofactors can be coenzymes or a prosthetic group. Because coenzymes are not securely attached to the apoenzyme, they can be easily removed from an enzyme’s active region. Cofactors include water-soluble vitamins or coenzymes like vitamin C and B, as well as minerals and elements including calcium, magnesium, iron, copper, zinc, and potassium. The apoenzyme is frequently loosely linked to prosthetic groups. Cofactors assist in the completion of processes that are not possible with ordinary enzymes. Small organic molecules like flavin or inorganic metal ions can be used as cofactors.

Conjugated Enzymes

A non-protein component called cofactor is necessary for biological action in a conjugate enzyme. When the cofactor is removed from a conjugate enzyme, a simple enzyme known as an apoenzyme is produced, which is physiologically inactive. A holoenzyme is a conjugated enzyme that is complete and biologically active (simple enzyme + cofactor). Covalent or non-covalent connections can be made between a cofactor and the enzyme’s protein component. Simple metal ions and complex organic groups, also known as coenzymes, are two types of cofactors. Prosthetic groups are cofactors that are strongly bound to a protein, either covalently or non-covalently.

Conjugate Proteins

A conjugated protein interacts with other chemical groups (non-polypeptide) via covalent bonding or weak interactions.

Simple proteins are those that include solely amino acids and no additional chemical groups. Other proteins, known as conjugated proteins, generate a chemical component other than amino acids when hydrolyzed. The prosthetic group refers to the non-amino portion of a conjugated protein. Vitamins are used to make the majority of prosthetic groupings. 

Non-protein moieties form covalent bonds with conjugated proteins.

Nucleoproteins, also known as deoxyribonucleoproteins (DNPs) or ribonucleoproteins (RNPs), are protein complexes that include nucleic acids. A common example of a DNP is the nucleosome, which is made up of nuclear DNA and histone proteins. The SARS-CoV virus’s primary antigen is an RNP that is required for virus genome replication.

Glycoproteins are a type of conjugated protein found on the surface of cells. Sugar residues projecting outwardly from the cell make up their short carbohydrate chain. Cell-cell adhesion, cellular recognition, and signal transduction all require the carbohydrate domain.

Lipoproteins are protein-lipid conjugates having a lipid core containing cholesterol, triglycerides, or both. Lipoproteins in mammals help insoluble lipids move from their production sites in the liver to other cells by facilitating the mass transfer. Lipoproteins are divided into numerous categories based on their densities. A portion of the complex becomes insoluble when the level of one or more lipoproteins grows too high. Insoluble lipoproteins can build up in the coronary artery and clog it, resulting in a stroke or heart attack.

Phosphoproteins, hemoproteins, flavoproteins, metalloproteins, phytochromes, cytochromes, and opsins are some of the additional conjugated protein kinds. Haemoglobin is a conjugate protein with iron in its heme prosthetic group that is important for oxygen transport in blood vessels.

Examples of Conjugate Proteins

A few examples of conjugated proteins are: –

• Lipoproteins, glycoproteins, nucleoproteins, phosphoproteins, hemoproteins, flavoproteins, metalloproteins, phytochromes, cytochromes, opsins, and chromoproteins.

Nucleoproteins:  When protein and nucleic acids are combined, they form a protein-nucleic acid complex. E.g., nucleohistones

Glycoproteins:  Proteins that arise in the presence of carbs. E.g., immunoglobulin

Metalloprotein: Metal-ion-containing proteins are proteins that contain metal ions in their molecules. e.g., Carbonic anhydrase

Lipoproteins: Proteins that have been lipid-conjugated. E.g., Lipovitellin of egg yolk

Phosphoproteins: Proteins that include a phosphorous group. E.g., Casein of milk

Chromoprotein: Combination of protein and prosthetic group – pigment. E.g., Hemocyanin

Conclusion

Enzymes are proteins that bind to substrate molecules and stabilise the transition state, lowering the activation energy required for a chemical process to take place. This stabilisation accelerates reaction rates, allowing them to occur at physiologically meaningful rates. Enzymes bind substrates to inactive sites, which are structurally important areas. They’re often highly specialised, binding just specific substrates for specific reactions. Without enzymes, most metabolic reactions would take much longer and would be too slow to sustain life. Understanding enzymes is crucial for detecting several diseases in medicine. In clinical studies, enzymes have been utilised as markers to identify disease states within the body. Doctors can often detect what type of illness a patient is suffering from and which organ is being affected by analysing the enzymes released into circulation. Tissue biopsies can also contain enzymes, which can provide useful diagnostic information.