No difference. Proteinase is the proper term, but protease has become a widely accepted alternative.
The alternative term for "sir" or "madam" is "ma'am."
An alternative term for "I am" in the English language is "I exist."
The alternative term for sugar in the field of biology is "carbohydrate."
The term crossbeam is an alternative for lintel.
Adhesive is the main alternative term for glue.
An arachnoid is an alternative term for an arachnid.
An amfetamine is an alternative term for an amphetamine.
An arseniuret is an alternative term for an arsenide.
An ameerate is an alternative term for an emirate, a place ruled by an emir.
An alternative word for the meteorological term, atmospheric, is sprays. An example of atmospherics is the spray of water droplets from a rushing waterfall.
The alternative term to "dear" that can be used to address someone in a formal letter is "respected."