Amino acid sequence of the active site of human pseudocholinesterase

The usualE ₁ ^u and atypicalE ₁ ^a human pseudocholinesterases (acylocholine acylhydrolase, EC 3.1.1.8) were purified to homogeneity. The active-site serine residue was conjugated with diisopropyl fluorophosphate and digested with trypsin. The tryptic peptide containing the active site was isolated by gel filtration followed by two-dimensional paper chromatography and electrophoresis. The amino acid sequence of the active site peptide obtained from the usualE ₁ ^u enzyme was found to be Gly-Glu-Ser-Ala-Gly-Ala-Ser-Ala-Val-Ser-Leu. A remarkable structural homology exists between the human and the horse enzymes in their active sites. From the difference in electrophoretic mobility of the active-site peptides obtained from the usual and atypical enzymes, the probable structure of the atypical human enzyme was deduced as Gly-His-Ser-Ala-Gly-Ala-Ser-Ala-Val-Ser-Leu.     

The nucleotide sequency of tRNA Gly from yeast

Analysis of the factor for proximity and orientation is given for cyclopentadiene dimerization and for the general case of more complex biological molecules. Using either a probability or a statistical mechanical approach, the same ratios are obtained. The proximity effect factor is found to be about $\text{55}\text{n}{}_{\mathrm{n}}$ per reacting pair of molecules which show no net attraction or repulsion. The use of translational entropy without inclusion of a rotational entropy term gives a misleading value for this proximity factor. The calculations support the argument that orientation factors can play a large role in the catalytic power of enzymes.