Enzymes as Indicators of Intracellular Reaction Conditions
153
These results support the conclusion that the kinetics of soluble enzymes is virtually the same in vivo as in vitro [9). Yet another conclusion can
be drawn from our experiments: urease is known to be located in the groundplasm of the plant cell and not bound to a structure [17] ; hence, the groundplasm must constitute a sYstem with the properties of an aqueous solution.
This conclusion is highly significant for the distribution of matter, e.g.
ions, between the cells and their surroundings. Further experiments are
needed; experiments with vital dyes have shown that the groundplasm
may behave also as a lipid sYstem [4, 7]. All the inferences for our present
knowledge of protoplasm cannot be discussed here; but it is evident that
enzyme systems are potent indicators of intracellular reaction conditions.
This fact could additionally be demonstrated with urease. We have
shown that urease is specifically inhibited in vitro by the antibiotic chloramphenicol (CAP) [18]. Consequently the actual free concentration of CAP
in the protoplasm can be determined by its effect on the urease reaction in
vivo; in short-term experiments this effect is independent of the inhibition
of protein synthesis by CAP. The results indicate that the effective concentration of CAP inside the cell is much lower than in the incubation medium.
This obviously results from an inactivation of CAP inside the cell [2, 20],
which may be one reason for the high resistance of many plant cells to this
antibiotic. The effective in vivo-concentration of CAP must be taken into
account when the sensitivity of protein synthesizing systems in vivo and
in vitro are compared.
References
1. CHANCE, B.: ]. BioI. Chem. 217, 409 (1955).
2. CZYGAN, F.-C.: Naturw. 51, 541 (1964).
3. DIXON, M.: Biochem.]' 55, 161 (1953).
4. DRAWERT, H.: In: Encyclopedia of Plant Physiology, Vol. II, p. 252,1956.
5. GUTFREUND, H.: An Introduction to the Study of Enzymes. Oxford 1965.
6. HESS, B., and K. BRAND: Clin. Chemistry 11, 223 (1965).
7. HOFLER, K.: Ber. dtsch. Bot. Gesellsch. 74,233 (1961).
8. HOLLDORF, A., und E. FORSTER: In: Die Zelle, Hrsg. METZNER, p.209.
Stuttgart 1966.
9. HOLZER, H.: In: Erg. med. Grundl.forsch., Vol. I, S. 189, 1956.
10. KISTIAKOWSKY, G. B., and A.]. ROSENBERG: ]. Amer. chem. Soc. 74, 5020
(1952).
11. LAIDLER, K. J.: Discuss. Faraday Soc. 20, 83.
12. McLAREN, A. D.: In: Cell Interface Reactions. Edit. BROWN, New York 1963.
13. MULLER, E.: Flora 148, 529 (1960).
14. - Nova Acta Leopoldina N. F. 24, Nr. 155 (1961).
15. - Flora 153, 549 (1963a).
16. - Protoplasm a 57, 611 (1963 b).
17. - Habil.-Schrift, Martin-Luther-Universitat. Halle 1966.
18. - Naturwiss. 54,226 (1967).
19. MYRBACK, K.: Acta Chem. Scand. 1, 142 (1947).
20. PARTHIER, B.: Naturwiss. 52,214 (1965).
153
These results support the conclusion that the kinetics of soluble enzymes is virtually the same in vivo as in vitro [9). Yet another conclusion can
be drawn from our experiments: urease is known to be located in the groundplasm of the plant cell and not bound to a structure [17] ; hence, the groundplasm must constitute a sYstem with the properties of an aqueous solution.
This conclusion is highly significant for the distribution of matter, e.g.
ions, between the cells and their surroundings. Further experiments are
needed; experiments with vital dyes have shown that the groundplasm
may behave also as a lipid sYstem [4, 7]. All the inferences for our present
knowledge of protoplasm cannot be discussed here; but it is evident that
enzyme systems are potent indicators of intracellular reaction conditions.
This fact could additionally be demonstrated with urease. We have
shown that urease is specifically inhibited in vitro by the antibiotic chloramphenicol (CAP) [18]. Consequently the actual free concentration of CAP
in the protoplasm can be determined by its effect on the urease reaction in
vivo; in short-term experiments this effect is independent of the inhibition
of protein synthesis by CAP. The results indicate that the effective concentration of CAP inside the cell is much lower than in the incubation medium.
This obviously results from an inactivation of CAP inside the cell [2, 20],
which may be one reason for the high resistance of many plant cells to this
antibiotic. The effective in vivo-concentration of CAP must be taken into
account when the sensitivity of protein synthesizing systems in vivo and
in vitro are compared.
References
1. CHANCE, B.: ]. BioI. Chem. 217, 409 (1955).
2. CZYGAN, F.-C.: Naturw. 51, 541 (1964).
3. DIXON, M.: Biochem.]' 55, 161 (1953).
4. DRAWERT, H.: In: Encyclopedia of Plant Physiology, Vol. II, p. 252,1956.
5. GUTFREUND, H.: An Introduction to the Study of Enzymes. Oxford 1965.
6. HESS, B., and K. BRAND: Clin. Chemistry 11, 223 (1965).
7. HOFLER, K.: Ber. dtsch. Bot. Gesellsch. 74,233 (1961).
8. HOLLDORF, A., und E. FORSTER: In: Die Zelle, Hrsg. METZNER, p.209.
Stuttgart 1966.
9. HOLZER, H.: In: Erg. med. Grundl.forsch., Vol. I, S. 189, 1956.
10. KISTIAKOWSKY, G. B., and A.]. ROSENBERG: ]. Amer. chem. Soc. 74, 5020
(1952).
11. LAIDLER, K. J.: Discuss. Faraday Soc. 20, 83.
12. McLAREN, A. D.: In: Cell Interface Reactions. Edit. BROWN, New York 1963.
13. MULLER, E.: Flora 148, 529 (1960).
14. - Nova Acta Leopoldina N. F. 24, Nr. 155 (1961).
15. - Flora 153, 549 (1963a).
16. - Protoplasm a 57, 611 (1963 b).
17. - Habil.-Schrift, Martin-Luther-Universitat. Halle 1966.
18. - Naturwiss. 54,226 (1967).
19. MYRBACK, K.: Acta Chem. Scand. 1, 142 (1947).
20. PARTHIER, B.: Naturwiss. 52,214 (1965).