Introduction Proteins play an important role in cellular fun
Proteins play an important role in cellular functions; however, being and remaining properly folded is necessary for their function. Understanding the stability of the protein is necessary to investigate the folding of proteins, as well as their conformation, functions and interactions with small ligands .
Elastase is a member of the serine proteases that does the catalysis of elastin analysis, a main component of the connective tissues. Two beta barrel areas are found in the active site of elastase, resulting in the hydrolyzed amides and the esters bonds of proteins. Pancreatic elastase is a main member of proteases with a compact globular structure and a hydrophobic core. Like other members of this family, the catalytic site of this enzyme has a serine residue. Elastase has three subunits each of which is attached to one calcium ion as a cofactor. The amino acids 77, 82 and 87 of elastase act as three main metal-binding sites . The active site of elastase is made of three hydrogen bonds inside the amino quinpirole residues of Histidine 71, Aspartic acid 119 and Serine 214; they are the basis of the cleaving ability of elastase. The chain of this enzyme has 240 amino acids and 4 disulfide bridges. It has a high scale of sequence similar to that of pancreatic elastases corresponding to other kinds, such as rats . The peculiar three-dimensional structure of elastase is a requisite for its activity; therefore, its activity can be affected by denaturation and/or conformational alterations.
Polyamines are one of the substances that can play an important role in cell growth. Polyamines are completely protonated at the physiological pH. They have a positive charge. Thus, they interact with other molecules such as proteins [4,5]. Due to the interaction of polyamines with proteins, contrarily charged, polar and aromatic residues are exceptionally vital. Polyamine compounds are little cationic particles which can be connected by electrostatic interactions to different macromolecules such as proteins and nucleic acids . Polyamines, whose charge pattern is expanded, are connected with proteins through their hydrophobic polyethylene backbone . The precursor of spermidine is putrescine. It is in all tissues together with nucleic acids. Spermidine is effective as a cation at all pH values and functions as a factor important for the stabilization of some membranes and nucleic acid structures. It is a precursor of spermidine too. Polyamines (such as spermidine) are used as co-solvents in biological and industrial applications requiring low-weight molecules [8,9].
Materials and methods
Results and discussion
Conclusions The experimental results demonstrated that the microenvironments of the tryptophan residue of elastase were changed by including diverse concentrations of spermidine. Spectrofluorometric results also demonstrated that with the addition of spermidine to the protein solution, the emission intensity of elastase was extremely diminished; then, by employing the Stern-Volmer equation, it was found that elastase quenching frequently occurred via static quenching. ∆G0 values determined at 303, 313 and 323 K were negative, showing that the process of binding of elastase to spermidine was a spontaneous molecular interaction. The thermodynamic parameters such as ∆H° and ∆S° were calculated to be negative, thereby showing that the interactions between spermidine and elastase were basically because of van der Waals forces or hydrogen bonding.
Acknowledgement The work was financially supported by Shahrekord University, Iran.
Introduction Proteases are one of the biocatalyst that has been widely studied because of the high demand in the industry. Since they are physiologically necessary and important for living organisms, proteases can be found in diverse sources such as plants, animals and microorganisms. However, proteases from the microbes are an attractive source due to the limited space used for their cultivation and their ready susceptibility to genetic manipulation. Pseudomonas aeruginosa is the most widely studied group of protease-producing microorganism . Pseudomonas sp. is known as an opportunistic pathogen, which often cause infection in the immunocompromised host  as its ability to produce proteolytic enzyme: elastase and alkaline protease [2,3]. Alkaline protease has broad cleavage specificity but it is not as potent as elastase and not hydrolyze elastin. Elastase, on the other hand, able to degrade proteins at multiple sites and host protein in addition to elastin. Since, it is active on elastin, this type of protease is called ‘elastase’. The elastase belongs to the natural metalloprotease  which require Zn2+ for its activity. Elastase was said to behave in a same manner as thermolysin from Bacillus subtilis due to the high degree of sequence similarity and functional homology . Nowadays, the enzymes are mostly used in industrial application. Their applications are increasing every year. Proteases remain the dominant industrial enzymes due to their extensive use in the detergent and dairy industries . Proteases application can also be found in leather, food and pharmaceutical industry purposes and also in bioremediation processes [6,7], apart from in the attractive applications of the proteases in biopharmaceutical products such as contact lens enzyme cleaners and enzymic debriders.