Re: How is shape of enzyme determined?

As you know, enzymes are proteins - biomolecules formed by an amino-acid 
chain. You find 20 common amino acids(aa's) in nature. Each functional 
protein is constituted by a specific order of aa's. A different aa order 
and/or nature effects the shape of the protein and finally its function. 
You need to know that each enzyme has its specific shape, determined by 
the primary aa sequence, which takes firstly, a "virtual" secondary 
structure, and finally a tertiary structure, the final structure of a primitive 
enzyme (other enzymes are constituted by several tertiary structures 
forming one fundamental biomolecule like hemoglobin for example).

How is an enzyme shaped?  The answer is not very simple. First thing to know is 
that each aa has specific chemical properties: some are acids others 
bases,etc...). Interactions between different aa of the sequence allow a 
specific shape: the nature of an interaction is different according the aa 
linked: for example ionic bonds, covalent bonds, or hydrogen bonds, etc.
The classical procedure to find out a structure is crystallographic 
diffraction study through X-rays and then computer treatment of the 
results (very complicated).

To conclude: each enzyme has a specific shape according to a specific 
function into the cell or not; a changing shape can affect the function of 
the enzyme (see Anfinsen's works on the ribonuclease); to stabilize the 
existing shape through weak interactions between aa, two sulfur-bearing 
(methyonin (rare) and cystein) aa's can establish a kind of "sulfur-bridge" 
for a strong interaction.  Unfortunately I don't have further infos about 
catalase: you find this enzyme in peroxysomes, special intracellular 
compartments involved in detoxification.  I can send you a picture of lysozyme, 
an enzyme also found essentially in lysosomes, other intracellular 
compartments.  You will have an example of enzyme shape.