Nucleoside phosphorylases are enzymes that play a crucial role in the metabolism of nucleosides, which are the building blocks of nucleic acids like DNA and RNA. These enzymes catalyze the reversible phosphorylation of nucleosides, converting them into their corresponding nucleobases and ribose-1-phosphate or deoxyribose-1-phosphate. This process is essential for recycling nucleotides and maintaining cellular nucleotide pools. These enzymes are found in various organisms, including bacteria, plants, and animals. They are important for cellular processes such as nucleotide salvage pathways, which help cells recover and reuse nucleotides, thereby conserving energy and resources. Nucleoside phosphorylases also have potential applications in biotechnology and medicine, particularly in drug development.