1,8-cineole synthase (CinS)

1,8-cineole synthase (EC 4.2.3.108) is a plant-derived monoterpene synthase responsible for the biosynthesis of 1,8-cineole, commonly known as eucalyptol [1, 6]. Found primarily in the secretory cells of aromatic plants such as Eucalyptus, Salvia officinalis (sage), and Rosmarinus officinalis, the enzyme catalyzes the conversion of geranyl diphosphate (GPP) into the symmetrical monoterpene ether 1,8-cineole [2, 4]. This catalytic process involves the isomerization of GPP to linalyl diphosphate, followed by cyclization to an alpha-terpinyl cation intermediate that is subsequently captured by water [4, 6]. While the enzyme itself is not a therapeutic target in human medicine, its product, 1,8-cineole, is a widely used pharmaceutical agent known for its anti-inflammatory, mucolytic, and antimicrobial properties in treating respiratory conditions such as asthma and chronic obstructive pulmonary disease (COPD) [8, 11, 15]. In the field of biotechnology, 1,8-cineole synthase is a primary target for metabolic engineering and synthetic biology efforts [7, 13]. Researchers utilize the enzyme's sequence and structural data to develop microbial cell factories for the sustainable large-scale production of high-purity eucalyptol, avoiding the environmental and seasonal constraints of traditional plant extraction [7, 10]. Furthermore, the enzyme's role in plant defense makes it a subject of study in agricultural science for developing natural pest-repellent strategies [10, 16]. Understanding the site-specific mutations, such as those involving active-site asparagine residues, allows for the rational design of the enzyme to alter product profiles for industrial applications [10].

Other names

Eucalyptol synthase1,8-cineole cyclaseGeranyl diphosphate diphosphate-lyase (cyclizing, 1,8-cineole-forming)1,8-cineole synthetaseCineole synthase

The enzyme catalyzes the cyclization of geranyl diphosphate to 1,8-cineole through a mechanism involving isomerization to (S)-linalyl diphosphate, ionization to the alpha-terpinyl cation, and stereospecific capture of the cation by a water molecule [4, 6, 10].