Nisin Raw Materials Price,Biosynthetic mechanism

Nisin, namely nisin of Streptococcus lactis, is a natural preservative. The following is an introduction to its chemical structure and biosynthetic mechanism.

I. Chemical Structure

Basic Skeleton

Nisin is a small peptide composed of 34 amino acids. Its main chain contains multiple amino acid residues, and these amino acids are sequentially linked by peptide bonds to form a linear structure.

Special Amino Acids

It contains 5 cyclic structures connected by thioether bonds, which are the rings formed between the amino acids at positions 1 - 4, 2 - 5, 4 - 6, 5 - 7, and 23 - 26. This cyclic structure endows Nisin with unique stability and biological activity.

Modified Amino Acids

It contains two uncommon amino acid modifications, namely lanthionine and β-methyl lanthionine. Lanthionine is formed by the dehydration condensation of the sulfhydryl groups of two cysteine residues and the hydroxyl group of a serine or threonine residue. This modification makes Nisin have stronger antibacterial activity and stability.

II. Biosynthetic Mechanism

The biosynthesis of Nisin is a complex process involving the participation of multiple genes and enzymes, which can be mainly divided into the following stages:

Gene Cluster Encoding

The synthesis of Nisin is encoded by the nis gene cluster located on the bacterial chromosome. This gene cluster contains multiple genes, which are respectively responsible for encoding various enzymes and regulatory factors required for the synthesis of Nisin. These genes work synergistically to ensure the smooth progress of its synthesis, modification, and secretion processes.

Precursor Peptide Synthesis

On the ribosome, the precursor peptide (pre-nisin) of Nisin is synthesized according to the information encoded by the nisA gene. The precursor peptide consists of three parts: a signal peptide, a leader peptide, and a mature peptide. The signal peptide is responsible for guiding the precursor peptide into the secretion pathway, the leader peptide plays an important role in the maturation and modification process of Nisin, and the mature peptide is the structure of Nisin with antibacterial activity.

Post-translational Modification

After the precursor peptide is synthesized, it will be recognized and acted on by a series of modifying enzymes for post-translational modification. These modifying enzymes include dehydratases, cyclases, etc. The dehydratase can catalyze the dehydration reaction of specific amino acid residues to form dehydrated amino acids; the cyclase catalyzes the formation of thioether bonds between the dehydrated amino acids and adjacent amino acids, thus constructing the cyclic structure in the Nisin molecule.

Transport and Secretion

The modified precursor peptide is transported outside the cell membrane. In the extracellular environment, the leader peptide is excised by specific proteases, and the mature Nisin is released. The mature Nisin is secreted outside the cell through the transport channels on the cell membrane to exert its antibacterial effect.

III. Influencing Factors

Gene Expression Regulation

The expression of the nis gene cluster is regulated by various factors, including the growth stage of bacteria, environmental conditions (such as pH value, temperature, nutrients, etc.), and the physiological state of host cells. These regulatory mechanisms ensure that Nisin is synthesized and secreted at the appropriate time and under the appropriate conditions.

Enzyme Activity

The activities of various enzymes involved in the synthesis and modification of Nisin will also affect the yield and quality of Nisin. For example, the activities of dehydratase and cyclase directly affect the formation of the cyclic structure in the Nisin molecule, thus affecting its antibacterial activity.