Proteinase K and protease are two types of protein-cleaving enzymes. While both are capable of cleaving peptide bonds in proteins, they differ considerably in the way they work and their uses. 

Proteinase K 

Proteinase K is a broad-spectrum serine protease enzyme that acts mainly on keratin protein. It plays a key role in digestion of proteins and eliminating contamination from nucleic acid preparations. 

Protease 

Protease is an enzyme catalyzing proteolysis. It acts mainly on the proteins in foods and plays a key role in multiple biological functions including cell signaling, digestion of ingested proteins, and protein catabolism.