The enzymatic synthesis of endomorphins were carried out by immobilized papain on sodium alginate-chitosan (IPSAC). The reaction has been carried out in two steps. First, Trp-Phe-NH2 was obtained by Boc-Trp-OH coupling with Phe-NH2 using IPSAC catalyst in microaqueous acetonitrile system with a 27.8 % yielding as determined by high performance liquid chromatography (HPLC). The catalytic properties of IPSAC were examined by studying the dependence of pH, ionic strength, solution content, reaction temperature,enzyme loading and reaction time over the yields. The results of orthogonal experiments indicated that pH was the most significant factor that influenced this synthesis. Second, Boc-Tyr-Pro-OMe and Trp-Phe-NH2 were suspended into the microaqueous acetonitrile to produce Tyr-Pro-Trp-Phe-NH2 (endomorphin-1) with a 35.2% yield.

In order to separate chiral D-phenylalanine from L-phenylalanine,the enzyme catalytic method by papain and immobilized papain were used in this investigation.It indicated that the yield rate of N-acetyl-DL-phenylalanine synthesized from DL-phenylalanine was 88.7%.The ionic strength was the strongest influencing factor in the synthesis of N-acetyl-L-phenylalanylaniline by both papain and immobilized papain on sodium alginate-ehitosan(IPSAC).But the reaction temperature was the strongest influencing factor in the synthesis by immobilized papain on nylon cloth(IPN).The ionic strength and the pH were the important influencing factors in the synthesis.The yield rates of the best synthesis system of N-acetyl-L-phenylalanylaniline by papain,IPSAC,IPN were 61.2%,54.7%,36.3%,respectively.The yield rate of L-phenylalanine from N-acetyl-L-phenylalanylaniline hydrolyzation was 59.2%.The optical purity of the product was 96.6%.The vield rate of D-phenylalanine from N-acetyl-D-phenylalanine hydrolyzation was 61.7%.The optical purity was 95.7%.