Proteins are a large group of nitrogenous compounds with high molecular weight, which play an important role in the physiological process and are essential for living organisms. They are composed of one or more chains of amino acids linked by peptide bonds in a particular order to establish the base sequence of nucleotide in the DNA coding for the protein. Each protein has a precise function and is essential for the regulation, functioning, and structure of the body's cell tissue and organ. Protein engineering is the process of developing valuable proteins or enzyme with a specific function. It is based on the use of the recombinant DNA technology for changing the amino acid sequence. It is used to produce enzyme in large quantities, for producing biological compounds, and to create a superior enzyme to catalyze the production of high value specific chemicals. Currently, various protein engineering methods are owing to the rapid development in biological science. Some of the methods used for protein engineering are rational design, site directed mutagenesis, random mutagenesis, homology modeling, cell surface display technology, molecular dynamics, and DNA shuffling technology. Mutagenesis and selection are effectively utilized for improving a specific property of an enzyme. Meanwhile, the rational design approach is the most classical method in the protein engineering market. It involves site-directed mutagenesis of the protein and allows introduction of specific amino acid into a target gene. Protein engineering has a variety of applications ranging from biocatalysis in food application, to medical, nano-biotechnology, and environmental applications. It is used in the detergent industry, food industry, biopolymer production, applications involving redox proteins and enzymes, medical applications, environmental applications, and nano-biotechnology applications. In medical applications, protein engineering is used for cancer treatment studies.