Histidine commercial preparation

Enzyme preparations from Clostridium perfringens and Escherichia coli are commercially available, and the latter enzyme [69] has been cloned, overexpressed [70-72], and crystallized [73]. Its spatial structure has been determined recently by X-ray crystallography at 2.2 A resolution which has revealed that the enzyme is a tetramer and belongs to the a//l-barrel class of proteins [74] (Fig. 4). The active site pocket is located at the carboxy-terminal end of the eight-stranded /1-barrel, and the reactive lysine residue, forming a Schiff base with pyruvate, has been identified to be Lysl65 (Fig. 5). However, the current X-ray model excludes the catalytic participation of a histidine residue [74],... 

Commercial EVAL hollow-fiber membranes prepared via the copolymerization of ethylene and vinyl alcohol have been recently explored for protein immobilization. L-Histidine has been coupled onto EVAL-fibers activated with epichlo-rohydrin or butanediol diglycidyl ether to prepare an affinity support for immunoglobulin G (IgG) purification [58]. Furthermore, histidine-immobilized hollow-fiber membranes have been employed for endotoxin removal from... 

This enzyme includes the amino acid of seiine-histidine-aspar-tame (Ser-His-Asp). The enz5me may be prepared as follows, or a commercial product may be used (53). 

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