The effect of triterpenes and flavonoids on the activity of several hyaluronic acid-splitting enzymes was investigated. Studies showed that the inhibitory effect of the triterpenes glycyrrhizin and glycyrrhetinic acid is dependent on the source of hyaluronate lyase. Hyaluronate lyase from Streptococcus agalactiae (Hyal B) and recombinant hyaluronate lyase from Streptococcus agalactiae (rHyal B) demonstrated strongest inhibition. In contrast, hyaluronate lyases from Streptomyces hyalurolyticus (Hyal S), Streptococcus equisimilis (Hyal C) and hyaluronidase from bovine testis (Dase) showed only reduced inhibition action. A non-competitive dead end inhibition with Ki=3.1+/-1.8x10(-6) mol/mL and Kii=6.7+/-2.4x10(-6) mol/mL was found for glycyrrhizin on recombinant hyaluronate lyase from Streptococcus agalactiae. The inhibitory effect of flavonoids on Hyal B, rHyal B and Dase was determined depending on the number of hydroxyl groups and side chain substituents in the molecule. Flavonoids with many hydroxyl groups inhibited hyaluronate lyase stronger than those with only a few. Native hyaluronate lyase (Hyal B) showed a more extensive inhibition than the recombinant protein (rHyal B). Accordingly, the inhibition by triterpenes and flavonoids is presumably specific for each hyaluronic acid (HA)-splitting enzyme.

The action of the plant products quassin, cinnamaldehyde and azadirachtin was examined using pharmacological and electrophysiological methods. All three substances inhibited the beat rate of the antenna-heart, with quassin causing a diastolic and cinnamaldehyde a systolic block. Quassin delayed and azadirachtin at first accelerated the frequency of action potentials in the heart muscle, but 5 · 10 )3 m of the latter compound degraded the spike pattern and decreased the heart rate. A typical prolongation of the duration of the action potentials was observed. In recordings from a nerve of the frontal ganglion, quassin and cinnamaldehyde reduced the intervals between the spontaneous bursts, which turned into a continuous spike discharge with a decline in activity, while azadirachtin had no effect. Measurements in a single neurone of this ganglion revealed that quassin had a suppressive effect on the frequency and amplitude of the action potentials. These results suggest that the physiological effects demonstrated do not cause the primary insecticidal actions of these plant products.

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The growth kinetics of batch cultures of the thiamine requiring Candida lipolyticu 695 was investigated. It was established that a phase of lo arithmic growth is followed by a linear growth phase. The time length of the linear phase and t t e relative increasing of the biomass during the linear phase are nearly constant and independend of the concentration of thiamine. The existence of the linear phase is discussed in connection with a constant activity of one of the two 2-ketoacid dehydrogenases as a bottle neck enzyme which needs thiamine pyrophosphate as coenzyme. Critical intracellular thiamine concentrations were calculated necessary for transition from the logarithmic to the linear phase and from the logarithmic to the stationary growth phase. Without the existence of the second critical thiamine concentration the linear growth would continue infinitely.

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