The inhibitory activity of angiotensin I-converting enzyme in milk increased during fermentation with the Calpis sour milk starter containing Lactobacillus helveticus and Saccharomyces cerevisiae. Two kinds of peptides inhibitory to angiotensin I-converting enzyme were purified from the sour milk by using four-step HPLC. The amino acid sequences of these inhibitors were identified as Val-Pro-Pro and Ile-Pro-Pro. The concentrations of peptides providing 50% inhibition of angiotensin I-converting enzyme were 9 and 5 microM, respectively. Most of the inhibitory activity in sour milk was attributed to these two peptides.
This study reports the antihypertensive effect of orally administered doses of either Calpis sour milk or peptides (Val-Pro-Pro and Ile-Pro-Pro), which are inhibitors to angiotensin I-converting enzyme, isolated from the sour milk using strain SHR spontaneously hypertensive rats. Single oral administration of the sour milk (5 ml/kg of BW), corresponding inhibitory units of the peptides Val-Pro-Pro (.6 mg/kg of BW), or Ile-Pro-Pro (.3 mg/kg of BW) significantly decreased the systolic blood pressure from 6 to 8 h after administration. Blood pressure returned to the initial level at 24 h after administration. Antihypertensive activity of these two tripeptides was dose-dependent up to 5 mg/kg of BW. Conversely, the sour milk (25 ml/kg of BW) and mixed tripeptides (10 mg each of Val-Pro-Pro and Ile-Pro-Pro/kg of BW) did not change the systolic blood pressure of the normotensive strain WKY Wistar-Kyoto rats.
Peptides derived from alpha s1- and beta-caseins by the Lactobacillus helveticus CP790 proteinase were investigated for their inhibitory activities against angiotensin I-converting enzyme. The antihypertensive effect of casein hydrolysates in strain SHR spontaneously hypertensive rats was also investigated. Both alpha s1- and beta-casein hydrolysates inhibited this enzyme. Some of these peptides showed enzyme inhibitory activity, and one of them from beta-casein inhibited the enzyme greatly; the concentration of an angiotensin I-converting enzyme inhibitor needed to inhibit 50% of the enzyme activity was 4 microM. The hydrolysate of casein demonstrated antihypertensive activity in spontaneously hypertensive rats at an orally administered dosage of 15 mg/kg of body weight. MILK fermented with L. helveticus CP790, containing about .3% peptides, also showed antihypertensive activity in SHR rats with 5 ml/kg of body weight (15 mg of peptide/kg); however, the milk fermented with L. helveticus CP791, a variant defective for proteinase activity, did not show this activity. Results suggested that the peptides liberated from casein by the proteinase in the culture medium showed antihypertensive effect in SHR rats.
Casein hydrolysate, produced by an extracellular proteinase from Lactobacillus helveticus CP790, was fractionated by two-step reverse-phase HPLC. Only one fraction showed antihypertensive activity as measured by systolic blood pressure in spontaneously hypertensive rats after oral administration. Ten peptides in the fraction were further purified and identified by analysis of amino acid sequences. Each identified peptide was chemically synthesized, and the antihypertensive activity of each peptide was evaluated in spontaneously hypertensive rats. The synthetic peptide with a sequence of Lys-Val-Leu-Pro-Val-Pro-Gln, found in beta-casein, indicated strong antihypertensive activity from 2 to 10 h after oral administration of 2 mg of peptide/kg of BW, and the effect was maximal at 6 h after oral administration (-31.5 +/- 5.6 mm Hg). Moreover, the antihypertensive effect of the peptide was dependent on the dosage of peptide from 0.5 to 2 mg of peptide/kg of BW. Interestingly, the antihypertensive peptide showed lower inhibitory activity of angiotensin I-converting enzyme, but the activity was increased after pancreatin digestion.
The Rice Annotation Project Database (RAP-DB) was created to provide the genome sequence assembly of the International Rice Genome Sequencing Project (IRGSP), manually curated annotation of the sequence, and other genomics information that could be useful for comprehensive understanding of the rice biology. Since the last publication of the RAP-DB, the IRGSP genome has been revised and reassembled. In addition, a large number of rice-expressed sequence tags have been released, and functional genomics resources have been produced worldwide. Thus, we have thoroughly updated our genome annotation by manual curation of all the functional descriptions of rice genes. The latest version of the RAP-DB contains a variety of annotation data as follows: clone positions, structures and functions of 31 439 genes validated by cDNAs, RNA genes detected by massively parallel signature sequencing (MPSS) technology and sequence similarity, flanking sequences of mutant lines, transposable elements, etc. Other annotation data such as Gnomon can be displayed along with those of RAP for comparison. We have also developed a new keyword search system to allow the user to access useful information. The RAP-DB is available at: http://rapdb.dna.affrc.go.jp/ and http://rapdb.lab.nig.ac.jp/.
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