摘要
研究了猪小肠中麦芽糖酶、蔗糖酶和乳糖酶 3种二糖酶的生化性质及活性分布。试验以 3头“杜加”生长猪为研究对象 ,屠宰并刮取胃底部、十二指肠、空肠上段和回肠黏膜。其中空肠黏膜用于 3种二糖酶生化性质的研究 ,包括酶的最适温度、热稳定性、最适 pH、pH稳定范围和金属离子对酶活性的影响 ;胃底部、十二指肠、空肠上段和回肠黏膜用于测定 3种二糖酶活性以揭示其在胃肠中的分布规律。试验结果表明 :麦芽糖酶、蔗糖酶和乳糖酶的最适反应温度分别为 5 0、 45和 5 5℃ ;最适 pH分别为 6 8、 6 5和 6 0 ;乳糖酶的耐热温度 (70℃ )高于麦芽糖酶和蔗糖酶 (5 0℃ ) ;不同pH对 3种二糖酶活性影响不大 ;金属离子Cu2 + 和Fe2 + 对 3种二糖酶均有激活作用 ;而Mn2 + 有抑制作用。此外 ,Zn2 + 能抑制麦芽糖酶活性 ,提高蔗糖酶活性 ,而不影响乳糖酶活性。 3种二糖酶活性在肠道中由高到低的分布为 :空肠、回肠、十二指肠和胃 ;其中麦芽糖酶在空肠和回肠中活性相近。回肠和空肠黏膜中的麦芽糖酶活性均显著高于十二指肠和胃中的酶活性 ,十二指肠酶活性显著高于胃 ;空肠中蔗糖酶和乳糖酶活性显著高于回肠、十二指肠和胃底部。从 3种二糖酶活性大小看 ,胃底部和十二指肠中的麦芽糖酶活性显著高于蔗糖酶和乳糖酶 ;
The properties and distribution of three gastrointestinal disaccharidases in pig, including maltase, sucrase and lactase, were studied. Growing pigs of Du Jia, a hybrid race, were used. Small intestine was removed immediately after slaughter. The mucosa from stomach fundus, duodenum, upper jejunum and ileum was scraped with a blunt side of knife. Mucosa samples (about 0 5 g) was homogenized with 4 0 ml of cold maleate buffer (0 1 mol/L, pH=6 8). The supernatant was collected by centrifugation (3 000 r/min, 10 min, 4℃) and used for determination of three disaccharidase activities and protein content. Jejunal mucosa extract was used to study the properties of three disaccharidases, including optimal temperature, heat stability, optimal pH, pH stability and the effects of metallic ions on enzymes activities. Disaccharidase activities from mucosal extracts were measured to investigate their distribution along gastrointestinal tract essentially according to the modified method of Dahlqvist (1968). The enzyme activities were determined by incubating 0 1 ml of properly diluted enzyme solution with 0 1 ml of 0 056 mol/L substrate (maltose, sucrose, lactose) for 30 min at 37℃. The reaction was terminated on a boiling bath. The released glucose amount was estimated by a Kit supplied by the Shanghai Institute of Biological Products. One unit of disaccharidase activity was defined as the amount of the enzyme that can hydrolyse 0 1 μmol/L of substrate equivalent per minute under the assay conditions. Protein content was determined according to the method of Bradford (1976) with bovine serum albumin as a standard. Maltase, sucrase and lactase had respective maximum activity at 50℃,45℃ and 55℃. After 30 min incubation at 55℃, maltase and sucrase retained 50% of their initial activity, and lactase retained 72%. After 30 min incubation at 72℃, maltase, sucrase and lactase retained 24 05%, 24 21% and 62 04% of their initial activity, respectively. So lactase was stable below 70℃, but maltase and sucrase were stable below 50℃. Maltase, sucrase and lactase had their optimum at pH 6 8, 6 5 and 6 0, respectively. Three disaccharidases had more than 80% residual activity between pH 3 0～8 0. All three disaccharidases were insensitive to pH. Metallic ions Cu 2+ and Fe 2+ could stimulate the activities of three disaccharidases, Mn 2+ had an inhibitory effect on these enzymes. Zn 2+ had a stimulatory effect on sucrase and the inhibitory effect on maltase. The distribution of three disaccharidases along the gastrointestinal tract in decreasing order was jejunum, ileum, duodenum, and stomach. There were no significant difference in maltase activities between ileum and jejunum, but higher than those in duodenum and stomach( P<0 01 ), and its activities in duodenum was higher than that in stomach( P <0 01). The sucrase and lactase activities in jejunum were higher than that in ileum, duodenum and stomach( P <0 01). The maltase activities were significant more than sucrase and lactase activities in stomach ( P <0 02)and duodenum( P <0 01). The maltase activities was significant more than sucrase( P <0 01), and sucrase more than lactase in jejunum and ileum( P <0 01).These results indicate that three gastrointestinal disaccharidases have different properties but similar distribution along the gastrointestinal tract.
出处
《动物学报》
SCIE
CAS
CSCD
北大核心
2002年第2期202-207,共6页
ACTA ZOOLOGICA SINICA
关键词
猪
二糖酶
性质
胃肠道黏膜
Pig, Disaccharidase, Properties, Gastrointestinal tract, Mucosa
