Bovine pancreatic lipase. II. Stability and effect of activators and inhibitors

Identification and characterization of two types of triacylglycerol lipase genes from Neocaridina denticulata sinensis

Triacylglycerol lipases (TGLs) can catalyze the hydrolysis reaction of triacylglycerol serving multiple functions in most organisms. Based on the genomic and transcriptomic databases of Neocaridina denticulata sinensis, two TGL genes from N. denticulata sinensis designated NdTGL1 and NdTGL2 were identified and characterized. NdTGL1 showed the highest expression in the stomach, followed by the testis and hepatopancreas, and NdTGL2 exhibited the maximum expression in the hepatopancreas, followed by the stomach and heart. Under the stimulation of copper ion, the expression of NdTGL1 peaked at 12 h and the expression of NdTGL2 elevated significantly at 24 h after stimulation (P < 0.05). It is speculated that NdTGLs may play an important role in the stress response of N. denticulata sinensis. Challenged with Vibrio parahaemolyticus, the expression profiles of NdTGL1 and NdTGL2 in the hepatopancreas was different, which indicates that the immune response of the V. parahaemolyticus challenge might lead to changes in triglyceride metabolism. The recombinant NdTGL (recNdTGL1 and recNdTGL2) were obtained and the enzymatic characterization of recNdTGL1 and recNdTGL2 were determined. The common maximum activity and stability of the recNdTGL1 and recNdTGL2 were observed at 45 °C and 10 °C, respectively. Both recNdTGL1 and recNdTGL2 exhibited the highest activity at pH 10.0. Furthermore, the recNdTGL1 and recNdTGL2 displayed the maximum stability at pH 5.0 and pH 8.0, respectively. In presence of different metal ions, the enzyme activity of recNdTGL1 and recNdTGL2 were inhibited by Cu²⁺ and Zn²⁺, and decreased by about 25%. Studies on the triacylglycerol lipases of N. denticulata sinensis provide theoretical support for studies related to fat metabolism in crustaceans and studies on response mechanism of digestive enzymes to microbial pathogens.

Partial characterization of pyloric-duodenal lipase of gilthead seabream (Sparus aurata)

In the present study, we report the isolation and characterization of seabream Sparus aurata pyloric caeca-duodenal lipase. Optimum activity was found at pH 8.5 and salinity of 50 mM NaCl. Lipase activity was sensitive to divalent ions, and extreme pH values (4, 5, and 12), being more stable at alkaline than acid pH. Optimum temperature was found at 50°C, but lipase was stable at temperatures below 40°C. Lipase has a bile salt sodium taurocholate requirement for increased activity. Gradient PAGE electrophoresis revealed the presence of four isoforms with apparent molecular masses of 34, 50, 68, and 84 KDa, respectively. Pyloric-duodenal lipase was able to hydrolyze emulsified alimentary oils. Results confirm the presence of true lipases in Sparus aurata digestive tract.

Further characterization of a novel triacylglycerol hydrolase activity (pH 6.0 optimum) from microvillous membranes from human term placenta

We recently identified the presence of two distinct triacylglycerol hydrolases with pH optima of 6.0 and 8.0 in human placental microvillous membranes (MVM). The TAG hydrolase with a pH optimum of 8.0 has properties similar to lipoprotein lipase, whereas TAG hydrolase with a pH optimum of 6.0 still to be fully characterized. In order to understand the functional and structural relationships between these two TAG hydrolases of MVM we have further investigated their biochemical and molecular properties. The presence of oleic acid inhibited TAG hydrolase activity with a pH optimum of 8.0 by 60 per cent whilst it had very little effect on the pH 6.0 TAG hydrolase activity. K(m)values for TAG hydrolases at pH 6.0 and pH 8. 0 optima were 170.6 and 9.83 nmol triolein, respectively, whereas the corresponding V(max)values were 0.32 and 0.037 nmol oleic acid/min mg/protein. Treatment of MVM with phenylmethylsulphonofluoride or protamine had no effect on TAG hydrolase at pH 6.0 whereas both decreased activity at pH 8.0, by 70 per cent and 52 per cent, respectively (P< 0.05), compared with control. p-Chloromercuribenzoate inhibited both TAG hydrolase activities by 25-30 per cent whereas iodoacetate inhibited TAG hydrolase activity with optimum pH 8.0 by 74 per cent and the activity at pH 6.0 by 28 per cent. Unlike the TAG hydrolase activity at pH 8.0, the activity at pH 6.0 was not affected by heparin. TAG hydrolase activity at pH 6.0 was significantly decreased compared with that of pH 8.0 optimum TAG hydrolase activity in smokers placenta. A threefold increase in pH 6.0 TAG hydrolase activity was observed following differentiation, whereas membrane associated TAG hydrolase activity with optimum pH 8.0 did not change. The TAG hydrolase with optimum pH 6.0 was subsequently purified from MVM to almost 1000-fold enrichment of the activity over the starting material. The final preparation however, still contained three distinct protein bands (90, 70 and 45 kDa). When extracted from non-denaturing polyacrylamide gels, the 70 kDa protein was the only protein to have TAG hydrolysing activity and had a pH optimum of 6.0. Labelling of samples with [(14)C]tetrahydrolipstatin also confirmed that the TAG hydrolase active protein was a 70 kDa protein. In conclusion, we report that there is a 70 kDa TAG hydrolase with optimum pH 6.0 in human placental MVM which is quite distinct from placental lipoprotein lipase.

Bovine pancreatic lipase. III. Lipolysis of oils and fats and fatty acid specificity

Purified bovine pancreatic lipase hydrolyzed butteroil, vegetable oils, and synthetic glycerides. The enzyme hydrolyzed triglycerides more rapidly than di- and monoglycerides and tripropionin faster than any other synthetic glyceride. Triacetin was the least hydrolyzed glyceride. Gas-liquid chromatographic analysis of the free fatty acids liberated by the lipase from milk fat indicated that the enzyme selectively liberated butyric acid in higher proportion than the relative amount originally in the fat. The enzyme released saturated as well as unsaturated fatty acids from commericial vegetable oils. With regard to the lipolytic behavior, in general, the bovine pancreatic lipase closely resembled milk lipase.