I would stick with your own rendering - to consitute here is used in the sense of to be considered to be something, to be a matter of, to amount to, etc., e.g.
constitute - to be considered to be something:
Failing to complete the work constitutes a breach of the employment contract.
http://www.ldoceonline.com/dictionary/constitute"does not consist of an inventive step/activity" just wouldn't be used here. It would be like saying "12 men consist of a jury". I'm not generally a fan of using the number of Google hits as a measure of anything very much, but I think it is helpful here - try Googling "consist of an inventive step" (3), then "constitute an inventive step" (4660) or "involve an inventive step" (130000).
Incidentally, is that really your entire sentence or is something missing? I would have expected a verb of some kind, e.g. using a ... in a ..., or adding a ... to a ... does not constitute an inventive step.
peer agreement (net): +3