Only a slight conformational change is enough to activate or deactivate a protein . Other things can activate or deactivate. Remember, all enzymes are proteins and an enzyme is needed for every single step of every single biochemical pathway - including protein synthesis . But not all enzymes are present in every cell all the time. They are synthesized as needed.
Every cell has a complete set of genes.
Proteins are synthesized when a gene is ' turned on '. Some proteins are soluble in H2O, some are not. The soluble ones can be transported to other cells in the plant. Remember, N is a mobile element, this is partly why. Two amino acids, methionine and cysteine also contain sulfur.