In this paper, we described a simple and single step procedure for the synthesis of horseradish peroxidise enzyme (HRP) capped silver and gold nanoparticles. HRP, a heme-containing enzyme utilises hydrogen peroxide to oxidise a wide variety of organic and inorganic compounds. The biosynthesized nanoparticles were characterized by means of UV-VIS spectroscopy, Dynamic light scattering (DLS), Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). FTIR study confirms the presence of peroxidase enzyme on the nanoparticles. Computational studies reveal that exposed amino acids (viz serine, threonine, arginine and glycine) play key role in reduction and as well as stabilization of nanoparticles. The HRP assisted silver and gold nanoparticles retained its biological activity in the nanoparticles. The study indicates that Peroxidase which is found in almost all the plants can be used for the large scale synthesis of nanoparticles. Moreover additional attraction is the retention of the enzymatic activity on the nanoparticles. In a single step reaction enzyme is catalysing and in doing so it gets immobilized on it. The integration of biomolecules to nanoparticles is a tedious method mainly due to the surface of nanoparticles. Functionalization of noble metal nanoparticles with biomolecules (e.g., protein and DNA) is in demand because such systems possess numerous applications in catalysis, delivery, therapy, and imaging, sensing and controlling the structure of biomolecules. Computational study highlighted the amino acids which are interacting with the metal ions, thus synthetic peptides can also be designed to synthesize the metal nanoparticles.