The earliest step is: a. joining amino-acids into a polymer like beads on a string (this order is the 'primary structure') b. the first part of the protein folds due to side-chain and backbone interactions c. enzymatic function is possible due to the completed tertiary structure creating an 'active site' region of the protein. d. the final protein tertiary structure is completed with the addition and folding of the last parts of the protein. e. formation of amino-acid building blocks

The earliest step is:

E.  Formation of Amino acid building blocks.

Explanation:

Most of the enzymes are proteins. They act as biocatalyst and alter the rate of biochemical reaction.

Proteins are unbranched polymers constructed from 22 standard α-amino acids.Amino acids act as monomers of protein and are composed of an amino group, a carboxyl group, a hydrogen atom and a distinctive side chain, all bonded to a carbon atom.Amino acid join together to form peptides and polypeptides.

Thus during the formation of a protein structure or an enzyme the sequence of step are as follows:

E. Formation of amino-acid building blocksA. Joining amino-acids into a polymer like beads on a string (this order is the 'primary structure')B. The first part of the protein folds due to side-chain and backbone interactions D. The final protein tertiary structure is completed with the addition and folding of the last parts of the protein.C. Enzymatic function is possible due to the completed tertiary structure creating an 'active site' region of the protein