腐敗性ならびに腐生性Pseudomonas属細菌のペクチン質分解酵素

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Studies on pectolytic enzymes secreted by Pseudomonas marginalis were conducted to elucidate a specific dissolution of pectic substances in infected host cell walls. Two isolates of pathogenic bacteria, N-6122 and N-6301, secreted pectic acid transeliminase (PATE), when grown on pectin-asparagine medium. Pectin esterase (PE) activity was extremely weak in culture filtrates. As for N-6301, the dialyzed filtrate also had a strong pectin trans-eliminase (PTE) activity, which reacts specifically to methylated pectin. In addition, weak polygalacturonase (PG) activity was found in this preparation. In the case of N-6122, these enzyme activities were not detected. From these results, it is concluded that polyuronide-chain spliting enzyme system in N-6122 obviously differs from N-6301. PATE and PTE showed maximum reaction velocity at pH 8.3 in Sφrensen borate buffer systems, when pectin was used as a substrate. PATE activity was remarkably accelerated by addition of 10^<-3> M CaCl_2, and completely inhibited by 10^<-4> M EDTA, using sodium-polypectate as a substrate. PTE activity was not apparently affected by these chemical compounds. Dialyzed culture filtrate of N-6122, mainly containing PATE, showed typical action to degradate plant tissues. When maceration activity was measured by per cent loss in dry weight of radish,' the preparation indicated an ability to decrease about 12% of sliced tissues, after incubation at 30C for 8 hours. The physical properties of tissue-macerating agent in dialyzed filtrate were similar to those of PATE. They responded in the same way to pH and temperature, viz. inactivation by lower or higher pH value and heating. From these reasons, it can be said that the tissue degradation in this preparation is, in part, attributable to an action of PATE, although the enzyme has not been purified to homogeneous state. In culture filtrates obtained from two saprophytic isolates of Ps. fluorescens, only a trace of trans-eliminase activity was detected. From these results, it is proposed that pathogenic pseudomonads are able to secrete pectolytic enzyme (s), causing degradation of plant tissues, but saprophytes have a little or no ability to produce them in this culture medium.
1973-12-25

腐敗性ならびに腐生性Pseudomonas属細菌のペクチン質分解酵素

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