There are three general methods to hydrolyze protein into its composition,amino acids.Those methods are acid hydrolysis,alkaline hydrolysis,and enzymatic hydrolysis.Strong acid is ordinarily the method of choice,and constant boiling hydrochloric acid,6 M,is most frequently used.The reaction is usually carried out in evacuated sealed tubes or under N2 (Nitrogen) at110 Celcius degree for 18 to 96 hours.Under these conditions,peptide bonds are quantitatively hydrolyzed (although relatively long periods are required for the complete hydrolysis of bonds to valine,leucine,and isoleucine).
While the complete alkaline hydrolysis of proteins,is achieved with 2 to 4 M sodium hydroxide at 100 Celcius degree for 4 to 8 hours.This is of limited application for routine analysis,because cysteine,serine,threonine,and arginine are destroyed in the process,and partial destruction by deamination of other amino acids occurs.The complete enzymatic hydrolysis of proteins is difficult,because most enzymes attack only specific peptide bonds rapidly.
Most proteinases or proteases will not completely break the proteins to amino acids,instead you have to combine a few enzymes for this purpose.Also,the enzyme(s) in the reaction will be left in the reaction.