Abstract
It is known that vitamin B1 is a growth factor for numerous bacteria and fungi including the yeasts (see the summary in Koser and Saunders (1938)). It has also been demonstrated that vitamin B1 is essential for the growth of the isolated roots of higher plants (Bonner, 1937; Robbins and Bartley, 1937). Because of this general vitamin B1 requirement of living organisms, it would seem a priori probable that the vitamin plays a role in some basic cellular process. That this is indeed the case was shown conclusively by the work of Peters and coworkers (see Peters and O’Brien (1938)) and of Lohmann and Schuster (1937). The latter workers found that the prosthetic group of yeast carboxylase is vitamin B1 pyrophosphate. In the case of yeast, vitamin B1 is, then, a constituent of a respiratory enzyme and vitamin B1 pyrophosphate is hence commonly referred to as “cocarboxylase,” a terminology used throughout this paper. Although considerable information is available concerning the role of vitamin B1 as a growth factor for roots, there is little known about the carboxylase of such roots. The present work was undertaken with the hope of elucidating possible relationships between vitamin B1 and the carboxylase of pea roots.
Highlights
A once precipitated pea root preparation was found to contain approximately 2.1 y of extractable cocarboxylase per gm. of dry weight. These findings indicate that pea roots contain a carboxylase similar in some respects to that found in yeast
That pyrophosphate is removed in the pyruvate inactivation of the enzyme is indicated by one experiment in which the supernatant fluid from the pyruvate treatment for removal of the coenzyme was found to contain no cocarboxylase, but this concentrated supernatant was still capable of reactivating treated pea root enzyme to some extent, a property possessed by pure pyrophosphate (Table II)
It is shown in the experiments reported above that pea roots contain a carboxylase capable of decarboxylating pyruvic acid
Summary
Roota supplied with 02 consumption per 100 mg. dry weight in 1 hr. 170 450 and dried superficially. That pyrophosphate is removed in the pyruvate inactivation of the enzyme is indicated by one experiment in which the supernatant fluid (concentrated to a small volume) from the pyruvate treatment for removal of the coenzyme was found to contain no cocarboxylase (was incapable of activating washed yeast), but this concentrated supernatant was still capable of reactivating treated pea root enzyme to some extent, a property possessed by pure pyrophosphate (Table II). The carboxylase activity measurements show that the pyruvate treatment caused inactivation of the preparation to the extent of 51 per cent This was completely reversed on addition of pyrophosphate, showing that no appreciable denaturation of the enzyme occurred. After equilibration the yeast was tipped in and the TABLE IV
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