There is an operator missing, likely a *:
-3.7 need_something_here (prof[x])
The "is not callable" occurs because the parenthesis -- and lack of operator which would have switched the parenthesis into precedence operators -- make Python try to call the result of -3.7 (a float) as a function, which is not allowed.
The parenthesis are also not needed in this case, the following may be sufficient/correct:
-3.7 * prof[x]
As Legolas points out, there are other things which may need to be addressed:
2.25 * (1 - math.pow(math.e, (-3.7(prof[x])/2.25))) * (math.e, (0/2.25)))
^-- op missing
extra parenthesis --^
valid but questionable float*tuple --^
expression yields 0.0 always --^