team up vs team

team up is not a noun while team is a noun.

Word	Noun	Adjective	Verb	Adverb
team up	No	No	Yes	No
team	Yes	No	Yes	No

As verbs, team up and team are synonyms defined as:

team up (noun)	team (noun)
	a cooperative unit (especially in sports)
	two or more draft animals that work together to pull something

team up (verb)	team (verb)
form a team	form a team