Salivary cystatins are a group of proteins that belong to the cystatin superfamily and are found in saliva. They function as inhibitors of cysteine proteases, which are enzymes that break down other proteins. Specifically, salivary cystatins help regulate the activity of these proteases in the oral cavity and protect the soft tissues of the mouth from degradation. There are several types of salivary cystatins, including cystatin A, B, C, D, SN, S, SA, and SB, each with different properties and functions. Some salivary cystatins have been studied for their potential role in oral health and disease, such as caries prevention and protection against oral cancer.

Cystatins are a group of proteins that inhibit cysteine proteases, which are enzymes that break down other proteins. Cystatins are found in various biological fluids and tissues, including tears, saliva, seminal plasma, and urine. They play an important role in regulating protein catabolism and protecting cells from excessive protease activity. There are three main types of cystatins: type 1 (cystatin C), type 2 (cystatin M, cystatin N, and fetuin), and type 3 (kininogens). Abnormal levels of cystatins have been associated with various pathological conditions, such as cancer, neurodegenerative diseases, and inflammatory disorders.