Michaelis Menten Hypothesis states that
Michaelis-Menten Theory (Enzyme-Substrate Complex Theory) 
Enzyme combines with a substrate to form a transient Enzyme-Substrate Complex which immediately break into Enzyme and products.
Rate of enzymatic reaction is independent of substrate concentration
Rate of non enzymatic reaction is proportional to substrate concentration
Km is the enzyme substrate complex association constant
Enzyme substrate complex formation is essential in enzymatic reaction.