If a mutation in the dna of a globular enzyme changed all of the leucine amino acids to isoleucine, predict how the relative position of the amino acid in the tertiary structure of the protein would be affected when the protein is placed in an aqueous solution.

Leucine (Leu) and essential amino acid (Ile) are unit isomers of each other with terribly similar structures and properties. They each have Hydrophobic facet chains of an analogous size. As each residues area unit H'phobic, they're going to attempt to bury themselves within the interior of the macro-molecule to minimize disruption to the water H-bonding network, driven by the Hydrophobic interaction. thus in wild kind and mutant protein, each Leu and Ile are going to be in very similar position. Because of them being isomers, they need similar facet chain geometries thus there will not be any issue with steric constraints, in order that they can each occupy a awfully similar area within the hydrophobic core of the macro-molecule.
As within the wild sort catalyst, Leu is within the situation, it's possibly concerned within the mechanism of the catalyst. but a Leu  mutation can conserve the properties of the residue that are necessary for chemical action. they're fairly nonreactive facet chains, thus are possibly concerned in binding of the substrate through the H'phobic interaction. thus the mutation might slightly decrease the affinity of the catalyst for the substrate, and reduce the speed of chemical action somewhat.