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<Trypsin> is a <serine protease>: an <enzyme> that performs <proteolysis> by catalysing <peptide bond> <hydrolysis>. It preferentially cuts on the <C-terminus> side of <lysine> and <arginine> <amino acid residues>, leaving the selected <amino acid residue> in the preceding fragment.<Trypsin from bovine pancreas, DPCC Treated (T1005) - Product Information Sheet (Sigma-Aldrich)>[Trypsin from bovine pancreas, DPCC Treated, T1005 product information sheet, p. 1: Product Description, serine-protease family and C-terminal cleavage specificity]{ref}

The bond being broken is the backbone <amide> linkage, rather than the <lysine> or <arginine> <amino acid side chain>. A formal connectivity equation for <hydrolysis> is
$$
\mathrm{R^1{-}C(=O){-}NH{-}R^2}+\mathrm{H_2O}
\longrightarrow
\mathrm{R^1{-}COOH}+\mathrm{H_2N{-}R^2}.
$$
Here $R^1$ and $R^2$ stand for the connected portions of the original <peptide>. Actual terminal <protonation> and <electric charge> depend on <pH>; the equation displays connectivity. <Water> supplies the elements needed to form the two new ends, while the <enzyme> is regenerated.

Selective cutting turns an unwieldy <protein> into shorter <peptides>, making <peptide mapping> useful for comparing <proteins>. In <cell culture>, <trypsin> also helps detach adherent <biological cells>: the <HeLa culture viability experiment> provides a concrete example of its use and subsequent stopping of <proteolysis>. The same <enzyme> can therefore serve both chemical analysis and preparation of a <biological cell> suspension.


 Trypsin (source code)