Heterocyclic amines are formed when the amino acids in the proteins react with sugar during the Maillard reaction when grilling.  When proteins are exposed to a high or low pH they will denature, or become chemically useless.  Most of the marinades have a pH of either 6, 7, and 8; either slightly acidic or slightly basic.  However, the lemon juice marinade has a pH of 2; implying that it will probably be the best inhibitor for the formation of heterocyclic amines because the lower pH will have a greater effect on the proteins that form the heterocyclic amines.