Oolong tea extract (OTE) was found to inhibit the water-insoluble glucan-synthesizing enzyme, glucosyltransferase I (GTase-I), of Streptococcus sobrinus 6715. The GTase-inhibitory substance in the OTE was purified by successive adsorption chromatography on Diaion HP-21 and HP-20 columns; this was followed by further purification by Sephadex LH-20 column chromatography. A major fraction that inhibited GTase activity (fraction OTF10) was obtained, and the chemical analysis of OTF10 indicated that it was a novel polymeric polyphenol compound that had a molecular weight of approximately 2,000 and differed from other tea polyphenols. Catechins and all other low-molecular-weight polyphenols except theaflavin derived from black tea did not show significant GTase-inhibitory activities. It was found that OTE and OTF1O markedly inhibit GTase-I and yeast a-glucosidase, but not salivary ol-amylase. Various GTases purified from S. sobrinus and Streptococcus mutans were examined for inhibition by OTE and OTF10. It was determined that S. sobrinus GTase-I and S. mutans cell-free GTase synthesizing water-soluble glucan were most susceptible to the inhibitory action of OTF10, while S. sobrinus GTase-Sa and S. mutans cell-associated GTase were moderately inhibited; no inhibition of S. sobrinus GTase-Sb was observed. Inhibition of a specific GTase or specific GTases of mutants streptococci resulted in decreased adherence of the growing cells of these organisms. The inhibitory effect of OTF1O on cellular adherence was significantly stronger than that of OTE.

Sesame peptide powder (SPP) exhibited angiotensin I-converting enzyme (ACE) inhibitory activity, and significantly and temporarily decreased the systolic blood pressure (SBP) in spontaneously hypertensive rats (SHRs) by a single administration (1 and 10 mg/kg). Six peptide ACE inhibitors were isolated and identified from SPP. The representative peptides, Leu-Val-Tyr, Leu-Gln-Pro and Leu-Lys-Tyr, could competitively inhibit ACE activity at respective Ki values of 0.92 microM, 0.50 microM, and 0.48 microM. A reconstituted sesame peptide mixture of Leu-Ser-Ala, Leu-Gln-Pro, Leu-Lys-Tyr, Ile-Val-Tyr, Val-Ile-Tyr, Leu-Val-Tyr, and Met-Leu-Pro-Ala-Tyr according to their content ratio in SPP showed a strong antihypertensive effect on SHR at doses of 3.63 and 36.3 microg/kg, which accounted for more than 70% of the corresponding dosage for the SPP-induced hypotensive effect. Repeated oral administration of SPP also lowered both SBP and the aortic ACE activity in SHR. These results demonstrate that SPP would be a beneficial ingredient for preventing and providing therapy against hypertension and its related diseases.

No abstract

Strepin P-l, a new proteinase inhibitor, is a low molecular weight peptide isolated from the culture fluid of Streptomyces tanabeensis (SAB-934). Strepin P-l strongly inhibited not only cysteine proteinases, calpain and papain, but also trypsin. The purification procedures included HP-20 adsorption chromatography, DEAE-cellulose, Amberlite CG-50, Sephadex LH-20 and G-25 column chromatography. The yield was 12 mg from 8 liters of culture fluid. The proteinase inhibitor thus prepared was a peptide composed of tyrosine, valine and argininal, that reacted positively with Sakaguchi and Pauly reagents on TLC. The N-terminal amino acid, tyrosine, was blocked with an isovaleryl group and the structure was elucidated to be AMsovaleryl-tyrosyl-valyl-argininal. The amino acid sequence-inhibitory activity relationships of strepin P-l , leupeptin and antipain toward calpain and papain are also discussed.