Isolation and Characterization of a Cysteine Protease of Freesia Corms

A protease, freesia protease (FP)-A, was purified to electrophoretic homogeneity from regular freesia (Freesia reflacta) corms in harvest time. The M _r of FP-A was estimated to be 24 k by SDS-PAGE. The optimum pH of the enzyme was 8.0 using a casein substrate. These enzymes were strongly inhibited by p-chloromercuribenzoic acid but not by phenylmethane-sulfonylfluoride and EDTA. These results indicate that FP-A belongs to the cysteine proteases. The amino terminal sequence of FP-A was similar to that of papain, and the sequences was regarded to the conservative residues of cysteine protease. From the hydrolysis of peptidyl-pNAs, the specificity of FP-A was found to be broad. It was thought that FP-A was a new protease from freesia corms.     

Purification and Characterization of a Cysteine Protease from Corms of Freesia,Freesia reflacta

A protease (freesia protease B) has been purified to electrophoretic homogeneity from corms of freesia, Freesia reflacta by five steps of chromatography. Its M_r was estimated to be about 26,000 by SDS–PAGE. The optimum pH of the enzyme was 6.0–7.0 at 30°C using casein as a substrate. The enzyme was strongly inhibited by p-chloromercuribenzoic acid but not by phenylmethanesulphonylfluoride and EDTA. These results indicate that freesia protease B is a cysteine protease. Nine sites of oxidized insulin B-chain were cleaved by freesia protease B in 24 h of hydrolysis. The four cleavage sites among them resembled those of papain. From the digestion of five peptidyl substrates the specificity of freesia protease B was found to be approximately broad, but the preferential cleavage sites were negatively charged residues at positions. Freesia protease B preferred also the large hydrophobic amino acid residues at the P₂ position, in a similar manner to papain. The amino terminal sequence of freesia protease B was identical with those of papain in regard to the conservative residues of cysteine protease.     

化学药剂预处理对小苍兰蕾期切花的保鲜效果

本文探明了8HQC(8—羟基喹啉柠檬酸盐)、STS(硫代硫酸银)、BA(6—苄基腺嘌呤)等化学药剂和蔗糖预处理对蕾期采收的小苍兰切花的保鲜效果。(1)各种药剂处理均可提高开花率及观赏品质,其中8HQC+STS+BA+蔗糖的组合效果最佳,开花率比对照提高37.6％,花径增大5.6毫米,瓶插寿命延长6.9天。(2)药剂预处理明显提高切花耐藏性,经处理的切花经3～5天冷藏后瓶插,其观赏品质和瓶插寿命仍显著高于未经处理和冷藏的对照组。品种间的耐藏性有差异。作者认为,药剂处理的显著作用之一是改善了切花体内的水份状况。     

小苍兰切花不完全开放的原因探讨及防止措施

本文探明了小苍兰切花瓶插过程中小花不完全开放的原因,是由于采收时切花体内自身糖分积累不足所致。用高浓度(10%,20%,30%)蔗糖液处理,可增加切花各主、侧花序含糖量,提高开放率并延长瓶插寿命。同时还研究了几种含糖、化学药剂及激素的瓶插液对小花开放、花色和瓶插寿命的效应,以S+8-HQC+KT(蔗糖+8-羟基喹啉柠檬酸盐+激动素)效果较佳。此外,还比较了糖液处理和化学药剂保鲜两种方法的利弊和应用范围。