Acetylcholinesterase is the primary cholinesterase of the body, meaning that it is one of the enzymes responsible for catalyzing the hydrolisis of esters derived from choline ([(CH3)3NCH2CH2OH]+), many of which are neurotransmitters; this process is relevant because if the neurotransmitters are not broken by the cholinesterase, homeostasis of their levels can be disturbed, which would cause synapses to be unable to rest.

Kinases catalyze phosphorylation (the transfer of phosphate groups to substrates), which is a process important for regulating protein function, activity and interactions, allowing cells to respond.

Ribulose-1,5-bisphosphate carboxylase/oxygenase, aka Rubisco, converts CO2 into organic carbon, fixating it on photosynthetic organisms. It is the most abundant enzyme on the Earth.It is sometimes considered slow and inefficient.

Papain is an enzyme coming majoritarily from Carica papaya latex, it can break proteins and has many applications, such as breaking tough meat fibers (thus making meat softer), dissociating cells in the first step of cell culture preparation, debriding (using enzymes to break collagens and remove necrotic tissue), tooth whitening, and some other minor ones.

Collagen is the body's most abundant protein on the body's connective tissues, not only on humans but for many animals. It is synthetized thanks mostly to vitamin C, as it acts as a cofactor (essential factor for an enzyme's catalysis, acting as an auxiliary for the active site) for the enzymes that stabilize the fiber. There are currently 28 types of human collagen described. It mantains strength, helps new cells grow, protect organs, makes skin elastic.