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A preparative scale synthesis of 15N-aspartic acid from fumarate and 15NH4OH catalyzed by immobilized aspartase has been developed. Immobilization of aspartase in membrane enclosed enzyme immobilization (MEEI) facilitates the separation of the enzyme from product and makes the enzyme stable and durable for multiple usage. A simple isolation procedure in total yield of 62% using perfusion ion exchange chromatography renders the procedure more practical. 相似文献
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I-Chun Lin Boonyaras Sookkheo Suree Phutrakul Shui-Tein Chen Min-Jen Tseng Kung-Tsung Wang 《中国化学会会志》1999,46(2):147-152
A combinatorial tetrapeptide library, Suc-Ala-Phe-Arg-AA1-OR, in which R = p-formamidobenzyl ester and AA1 = 17 of the 20 natural occurring amino acids, has been synthesized chemically and separated by a reverse phase HPLC. The library was used to study the s-1 subsite specificity of various proteases. The preferred substrate at the s-1 subsite of chymotrypsin is in the order of Trp > Tyr > Phe > Met > Leu. This agreed with the reported data that the favored substrate at the s-1 subsite for chymotrypsin-catalyzed hydrolysis is an aromatic amino acid residue. The hydrophobic amino acid residues at this subsite can be hydrolysized after a longer incubating time. This procedure of selective hydrolysis of a peptide library was used to probe the selectivity of s-1 subsites of four proteases isolated from Bacillus stearothermophilus, subtilisin Carlsberg, subtilisin BPN' and an engineered protease subtilisin 8397. The protease from Bacillus stearothermophilus favored the substrate with residue Lys, and Arg at the s-1 subsite as a trypsin-like protease. The relative reactivities of amino acid residues in the protease-catalyzed hydrolysis of the library can be used as a fingerprint to identify the protease in a protease family. 相似文献
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