Coproporphyrinogenase in tobacco (Nicotiana tabacum L.)

1. Coproporphyrinogenase was extracted and purified from tobacco (Nicotiana tabacum L.). Enzyme activity was mainly located in mitochondria rather than in chloroplasts. The enzyme was purified by differential centrifugation, ammonium sulphate fractionation, calcium phosphate gel adsorption and dialysis. A 69-fold final purification was obtained. 2. An apparent Km value of 3.6×10−5m was found, the value being largely dependent on the amount of coproporphyrin III recovered after reduction with sodium amalgam to coproporphyrinogen III. Protoporphyrin formation was linear up to 3h and decreased with further incubation. The enzyme activity increased with the concentration of enzyme protein up to 30μg/ml of solution. 3. Enzyme activity was greatly enhanced by increasing Fe2+ concentrations up to 0.5mm, beyond which inhibition occurred. Co2+ and Mn2+ were also found to activate at low concentrations (0.1mm) and inhibit at higher concentrations (5mm). Fe3+ and Cu2+, both at 0.1mm, and o-phenanthroline and EDTA, each at 1mm, were found to be inhibitory.

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Change of Antioxidant Enzyme Activity during Low-Temperature Hardening of Nicotiana tabacum L. and Secale cereale L.

Russian Journal of Plant Physiology ◽

10.1134/s1021443720050118 ◽

2020 ◽

Vol 67 (5) ◽

pp. 898-905

Author(s):

V. N. Popov ◽

N. V. Naraikina

Keyword(s):

Enzyme Activity ◽

Nicotiana Tabacum ◽

Low Temperature ◽

Antioxidant Enzyme ◽

Secale Cereale ◽

Antioxidant Enzyme Activity ◽

Nicotiana Tabacum L ◽

Secale Cereale L ◽

Temperature Hardening

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Thymidylate kinase from Acetabularia. I. Properties of the enzyme

Journal of Cell Science ◽

10.1242/jcs.64.1.13 ◽

1983 ◽

Vol 64 (1) ◽

pp. 13-25 ◽

Cited By ~ 1

Author(s):

E.J. de Groot ◽

H.G. Schweiger

Keyword(s):

Enzyme Activity ◽

Kinase Activity ◽

High Specificity ◽

Test System ◽

Temperature Optimum ◽

Cell Fragment ◽

Low Concentrations ◽

Km Value ◽

A Cell ◽

Acetabularia Mediterranea

The occurrence of a dTMP kinase as well as a dTDP kinase in Acetabularia mediterranea has been demonstrated. A test system was developed by which it was possible to estimate the enzyme activity in an individual Acetabularia cell or even in a cell fragment. The enzyme catalyses the phosphorylation of dTMP in the presence of ATP. In the test system described, dTTP is formed as well as dTDP. This indicates that there is also a dTDP kinase present in the enzyme preparation. Characteristics of the enzyme such as pH optima at pH 7.0 and 8.75, a temperature optimum at 45 degrees C, a Km value of 3.3 X 10(−6) M and a high specificity for ATP were established. In homogenates that were preserved at −70 degrees C the enzyme activity was retained even after many weeks. Freezing at −70 degrees C and then thawing resulted in an increase in enzyme activity. The enzyme was inhibited by low concentrations of dTTP. After centrifugation of homogenates the greater part of the enzyme activity was found in the sediment. From the observation that purified chloroplast preparations contained most of the dTMP kinase activity, and that chlorophyll and enzyme activity cosedimented in a linear sucrose gradient, it was concluded that the enzyme is located in the chloroplasts.

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