Which one of the following is not an enzyme?

Amylase, pepsin, and trypsin are all digestive enzymes. Amylase is secreted by the salivary glands and pancreas to break down carbohydrates [t1, t6]. Pepsin is a protein-digesting enzyme produced in the stomach that functions optimally in an acidic environment [c2, t8]. Trypsin is a protease secreted by the pancreas that aids in protein digestion within the small intestine [c1, t4]. In contrast, somatotropin (also known as human growth hormone or hGH) is not an enzyme but a polypeptide hormone [t3, t9]. It is secreted by the somatotroph cells in the anterior pituitary gland and is essential for regulating body growth, linear bone development, and metabolism [t2, t9]. While enzymes act as biological catalysts for chemical reactions like digestion, somatotropin acts as a signaling molecule that binds to receptors to regulate physiological processes [t3].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 5: Life Processes > Activity 5.3 > p. 85
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 5: Life Processes > Activity 5.3 > p. 86
3. [3] https://deadiversion.usdoj.gov/drug_chem_info/hgh.pdf