It was my intention at the outset to include a phylogram which would compare the sequence homology of the three proteins studied. Upon submitting the amino acid sequences for optimal alignment it was discovered that there was less than 3% sequence homology. Thus they are structurally unrelated and the inclusion of this data would be meaningless. However from this examination as a whole, much was learned. Choosing a hydrolase from the thousands of solved structures was one of the hardest parts of this process. One from a bacterium, a plant, and a human were chosen to hopefully highlight this class of enzymes great diversity. Their diversity demonstrates their necessity to all living things. Also each of these enzymes acted on chemically diverse substrates and each utilized a different cofactor. This point is an excellent illustration of evolution. From the simple E. coli to the complicated human hydrolases are crucial enzyme that every living thing discovered takes advantage of. There are some key similarities and differences worth noting.
With enzymes as with anything form and function find themselves intimately bound, this is no different with hydrolases. From a check of sequence homology it was found that 3% of the residues were homologous. It is quite interesting that although all of these enzymes were hydrolases they all had evolved quite independently to bind their respective substrates.
Really the most important similarity is the most obvious one, that being that they are all hydrolases. This means that no matter how diverse the substrates, they are all going to to the same thing to it. Split a water molecule and stick a proton to one end and a hydroxly group to the other. The other significant similarity lies in the active site. They all have a residues with sidechains in the active site that show a good degree of charge separation. That is the side chain is polar. (In barley alpha amylase these polar residues were Asp180, Glu205, & Asp91; for Epoxide hydrolase it was Asp333, and in Alkaline Phosphatase they were Ser102 & Arg166). Under normal circumstances the presence of polar molecules near any of the respective substrates would not be sufficient to cause any reaction with water. However when these polar sidechains are in an enzyme binding of substrate orients the molecule in such a way that the probability of a reaction is exponentially increased.
Back to Index
Note to visitors if you like what you see that is great because it was all free! If you think you would like to build a website like this then here is a page that can get you started on downloading the tools you'll need.