Structure of Chlorodesoxypatulinic Acid
BERGEL et al.1 found that the product of the action of ethanolic hydrogen chloride on patulin gave on hydrolysis a crystalline chloro-acid, C7H7O4Cl, now called Chlorodesoxypatulinic acid. Afterwards, Plattner et al.2 observed that the same acid was readily produced by the action of hydrogen chloride on patulin in moist ethereal solution. The expression (I) was originally deduced1 for Chlorodesoxypatulinic acid from its relationship to patulin, for which the structure (II) was assumed3. Recent developments in this Laboratory and in that of Plattner necessitated the abandonment of these views, and led the Swiss group2 to formulate Chlorodesoxypatulinic acid as (III), which was consonant with either of two new structures, (IV)4 and (V)2, put forward for patulin in Cambridge and in Zurich, respectively. We have now accumulated new evidence which requires that (III) in its turn be rejected, and which leads to a new view of the structure of chlorodesoxypatulinic acid which is consistent only with the structure (IV) for patulin.
Desoxypatulinic acid from a patulin-producing strain ofPenicillium patulum
Aus Kulturlösungen vonPenicillium patulum Bainier wurde neben Patulin die Desoxypatulinsäure isoliert und identifiziert.
New method for analysis of enzymatic reactions: Thermolysin-catalyzed synthesis of aspartame precursor
Aspartame is an artificial sweetener which is 200 times sweeter than sucrose. A precursor of aspartame, N-(benzyloxycarbonyl)-l-aspartyl-l-phenylalanine methyl ester (Z-APM) was synthesized and hydrolyzed with thermolysin in an aqueous monophasic system. Graphical plotting methods and/or nonlinear regression have been used to analyze enzymatic reactions because of the nonlinearity of enzymatic rate equations. There are, however, problems: the former require accurate measurement of the initial reaction rate and the latter gives no analytical information. The authors proposed a method to solve the nonlinear enzymatic rate equations with respect to the concentration of a product with the Taylor expansion, especially for the reversible Theorell-Chance mechanism (Murakami, Y., Hirata, M., and Hirata, A., J. Ferment. Bioeng., 82, 246–252, 1996). This solution, however, is complex for practical use. In this paper, a simpler solution to explain the thermolysin-catalyzed synthesis of Z-APM is obtained. New methods to determine the kinetic parameters, especially for the reversible Theorell-Chance mechanism, based on the approximated solution are proposed. The results calculated using the obtained kinetic parameters can satisfactorily explain the experimental results, which demonstrates the effectiveness of the proposed analysis. We must know the relation between the concentrations of substrates and a product, and accurately evaluate of the result obtained using Taylor expansion when we determine the kinetic parameters using our newly developed methods. The methods to determine the kinetic parameters of the reversible Theorell-Chance mechanism described in this paper is, however, expected to be applied to general enzymatic reactions.