Synthase is an enzyme that catalyzes the synthesis of new compounds in the body. Because of this, it is an incredibly common and diverse enzyme found throughout both higher and lower order species.
It is important to note that the definition of what constitutes a synthase has changed over time. Initially, there was a difference in the biological nomenclature that differentiated synthases and synthetases. Synthases, under the original definition, did not use energy from nucleotide triphosphates, like ATP, while synthetases did.
However, the Joint Commission on Biochemical Nomenclature updated the definition, describing a synthase as any enzyme that catalyzes synthesis, regardless of energy source. They then went on to decree that synthetases are now synonymous with ligase.
Monoterpene synthases are found in plants and help them create the terpenes that they need to defend themselves against the threats in their environment. Interestingly, synthases can be used to create an enormous variety of structures within the plant, with some species constructing more than one thousand individually-identifiable structures in their development.
Synthase is also crucial in capsule structure, synthesis, and regulation. Researchers publishing in Streptococcus Pneumoniae in 2015 found that synthase CPS biosynthesis, as used by serotypes 3 and 37, is very different from the mechanisms described in the past.
Some synthases are also employed in the human and animal nutrition industry. Pfa synthase, for instance, is an example of FAS/PKS biosynthetic logic that can produce a variety of molecules with lots of economic applications. Commercial exploitation of synthases in single-cell production operations, for instance, could lead to the development of cheaper and more energy-efficient ways to produce biochemical products.
Synthases interact with other compounds in biological structures in a variety of ways. In synthase CPS biosynthesis, CPSs attach to the cell via a phosphatidylglycerol membrane anchor or the synthase enzyme. Hence, in synthase-dependent CPS biosynthesis, a single enzyme is responsible for multiple steps in the polymerization of polysaccharides. Thus, not only does synthase initiate the biosynthesis itself, but it also connects chains of molecules and then provides a mechanism for distributing them to other tissues external to the site of synthesis.
The precise way in which synthases work is still a matter for scientific investigation.
The early work on synthase mechanisms focused on substrate analogs containing 5-fluorouridine. Initial investigations suggested the “Michael mechanism,” which involved the addition of catalytic Asp and C6 to the pyrimidine ring of the isomerized uridine.
More recent work, however, throws these conclusions into doubt. The idea since Miracco and Mueller in 2011 points towards the “glycal mechanism.” The researchers posited this new mechanism after observing the epimerization at the C2’ site of the ribose ring of 5-fluorouridine in RNA. The experiment showed that the only way to explain the enzymatic activity was through the deprotonation of C2’ and then re-protonation using a glycal intermediate. Without the glycal mechanism, it is unclear how such a reaction could take place.