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Biosynthese aliphatischer Monoamine in Bliitenpflanzen durch Nebenaktivitat einer Glutamat-Oxalacetat-Aminotransferase?

1976; Elsevier BV; Volume: 77; Issue: 3 Linguagem: Inglês

10.1016/s0044-328x(76)80202-4

0044-328X

W. Üger, Tobias Hartmann,

Microbial Metabolites in Food Biotechnology

An Enzyme System Which Catalyzes The Transamination Between Amino Acids and Aliphatic Monoaldehydes (Aat-System) Has Been Purified 58-Fold From Spinach Leaves By Ammonium Sulfate Fractionation, Ion Exchange Chromatography On Deae-Sephadex-A-25 and Gel Filtration On Sephadex-G-200. During The Purification Process The Aat-System Has Been Successfully Separated From Several Other Transaminases I.E. Glutamate-Pyruvate-Transaminase (Gpt) and An Isoenzyme Of Glutamate-Oxaloacetate-Transaminase (Got-Ii). But A Second Got Isoenzyme (Got-1) and A System Which Catalyzes A Leucine-A-Ketoglutarate-Transamination (Lkt) Were Eluted Exactly In The Same Fractions As The Aat-System With Ion Exchange Chromatography and Gel Filtration. Both Activities Were Co-Purified With The Aatsystem. Separation Of The Purified Preparations By Disc Gel Electrophoresis Established The Same Band Position For Got-I and Aat On Polyacrylamide Gels. In Purified Preparations The Activity Ratio Of Got-I/Aat Is 525 : 1. This ratio is not altered significantly during the last two purification steps. In addition the AAT-system as well as the GOT-I have a pH optimum of 8.1, and showed the same degree of coenzyme dissociation after preincubation with glutamate. By contrast the LKT-system had a optimal pH of 8.4, and differed significantly in the coenzyme affinity. It is assumed that the LKT activity is catalyzed by an individual protein. L-Alanine was found to be the most efficient NH,-donator for the AAT catalyzed reactions. In the presence of alanine all aldehydes of the homologous series from ethanal to octanal were aminated to yield the corresponding amines. The results support the assumption already discussed in preceeding papers (HARTMANN et al., 1972 a and b) that the AAT-system which catalyzes the amine formation in higher plants and which has been shown to occur in all plants regardless whether they are amine producers or not, might be due to minor activity of an ubiquitous transaminase. This transaminase could be the GOT-I. Ein Transaminasesystem, das aliphatische Monoaldehyde zu den entsprechenden Aminen umsetzt (AAT-System), wurde aus Spinatblattern 58fach gereinigt. Das AAT-System ließ sick im Reinigungsgang nicht von einem Isoenzym der Glutamat-Oxalacetat-Transaminase (GOT-I) and einer Leucin-a-Ketoglutarat-Transaminase (LKT) trennen. Es ließ sick jedoch sichern, daß die LKT-Aktivität durch ein eigenes Protein katalysiert wird. Im gereinigten Präparat beträgt das GOT- I/AAT-Aktivitätsverhältnis 525 : 1. AAT and GOT-1 verhalten rich in allen überprüften Eigenschaften (Temperaturstabilität, pH-Optimum, Coenzymaffinität) völlig gleich. Das AAT-System katalysiert mit Alanin als bestem NH2-Donator die Aminierung aller aliphatischer Aldehyde von Äthanol bis Octanal. Sehr wahrscheinlich sind die AAT-Reaktionen auf Nebenaktivität der GOT-1 zurückzuführen.