<abstract xmlns="http://www.w3.org/1999/xhtml">The activity of 1-aminocyclopropane-1-carboxylic acid oxidase (ACO; EC 1.4.3.3) in germinating seeds of <italic>Callistephus chinensis</italic> was studied. For maximum recovery of ACO activity <italic>in vitro</italic>, the presence of 10% (w/v) insoluble polyvinylpolypyrrolidone (PVPP) and 30% of glycerol in the extraction medium was necessary. The optimum pH for this activity was 7.0. Ethylene production by whole achenes or enzymatic extract increased due to increasing 1-aminocyclopropane-1-carboxylic acid (ACC) concentrations. Saturation level of ACC for <italic>in vivo</italic> ACO activity was 10−1 M and Vmax was 10.89 nL C2H4·mg protein−1·h−1. For <italic>in vitro</italic> ACO activity, the saturation level of ACC was 10−3 M and Vmax was 2.299 nL C2H4·mg protein−1·h−1. Both, <italic>in vivo</italic> and <italic>in vitro</italic> ACO activities did not follow Michaelis-Menten kinetics. The Hill coefficients (<italic>h</italic>) were estimated on the basis of non-linear estimation. Their values were 0.63 for <italic>in vivo</italic> ACO activity and 1.73 for <italic>in vitro</italic> ACO activity. The experimental data show that ACO from <italic>C. chinensis</italic> seeds is an oligomeric enzyme with at least two active sites. During seed germination, <italic>in vitro</italic> ACO activity was detectable after 12 hours of imbibition, while <italic>in vivo</italic> ACC conversion to ethylene was observed after 24 h, i.e. – after radicle protrusion. The activity of ACO in <italic>C. chinensis</italic> seeds is associated with germination <italic>sensu stricto</italic>, and might be a good marker of this process.</abstract>

The activity of 1-aminocyclopropane-1-carboxylic acid oxidase (ACO; EC 1.4.3.3) in germinating seeds of Callistephus chinensis was studied. For maximum recovery of ACO activity in vitro, the presence of 10% (w/v) insoluble polyvinylpolypyrrolidone (PVPP) and 30% of glycerol in the extraction medium was necessary. The optimum pH for this activity was 7.0. Ethylene production by whole achenes or enzymatic extract increased due to increasing 1-aminocyclopropane-1-carboxylic acid (ACC) concentrations. Saturation level of ACC for in vivo ACO activity was 10−1 M and Vmax was 10.89 nL C2H4·mg protein−1·h−1. For in vitro ACO activity, the saturation level of ACC was 10−3 M and Vmax was 2.299 nL C2H4·mg protein−1·h−1. Both, in vivo and in vitro ACO activities did not follow Michaelis-Menten kinetics. The Hill coefficients (h) were estimated on the basis of non-linear estimation. Their values were 0.63 for in vivo ACO activity and 1.73 for in vitro ACO activity. The experimental data show that ACO from C. chinensis seeds is an oligomeric enzyme with at least two active sites. During seed germination, in vitro ACO activity was detectable after 12 hours of imbibition, while in vivo ACC conversion to ethylene was observed after 24 h, i.e. – after radicle protrusion. The activity of ACO in C. chinensis seeds is associated with germination sensu stricto, and might be a good marker of this process.

<italic>In vivo</italic> and <italic>in vitro</italic> Activity of 1-aminocyclopropane-1-carboxylic Acid Oxidase in Germinating Seeds of China Aster (<italic>Callistephus chinensis</italic> Nees)

Journal of Horticultural Research

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

 and  Activity of 1-aminocyclopropane-1-carboxylic Acid Oxidase in Germinating Seeds of China Aster ( Nees)

The activity of 1-aminocyclopropane-1-carboxylic acid oxidase (ACO; EC 1.4.3.3) in germinating seeds of Callistephus chinensis was studied. For maximum...

ACC oxidase activity	V_max (nL C₂H₄·mg protein⁻¹·h⁻¹) ± SE	K_m for ACC (μM) ± SE	Hill coefficient h ± SE
In vivo	10.89 ± 1.13	368 ± 92	0.63 ± 0.097
In vitro	2.299 ± 0.14	154 ± 20	1.73 ± 0.39

PVPP	NaHCO₃	Ethylene (nL·mg protein⁻¹·h⁻¹)	Increment (%)
5%	-	1.086 a ± 0.042	-
5%	25 mM	1.158 a ± 0.154	6.6
10%	-	1.246 a ± 0.073	16.4
10%	25 mM	1.925 b ± 0.217	77.0

In vivo and in vitro Activity of 1-aminocyclopropane-1-carboxylic Acid Oxidase in Germinating Seeds of China Aster (Callistephus chinensis Nees)

Published Online: Dec 31, 2020

Page range: 11 - 20

Received: Apr 01, 2020

Accepted: Oct 01, 2020

DOI: https://doi.org/10.2478/johr-2020-0021

Keywords
ACC oxidase, ACO, germination

© 2020 Mariusz Chojnowski et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Figure 1

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Figure 5

Apparent Vmax, Km and Hill coefficient h of ACC oxidase from Callistephus chinensis seeds analyzed in vivo and in vitro at 25 °C

Effect of PVPP and NaHCO3 on in vitro activity of ACC oxidase from Callistephus chinensis seeds germinated for 48 h. Means followed with the same letter are not significantly different at p = 0.05 according to Duncan's test; mean ± SE

In vivo and in vitro Activity of 1-aminocyclopropane-1-carboxylic Acid Oxidase in Germinating Seeds of China Aster (Callistephus chinensis Nees)

Published Online: Dec 31, 2020

Page range: 11 - 20

Received: Apr 01, 2020

Accepted: Oct 01, 2020

DOI: https://doi.org/10.2478/johr-2020-0021

KeywordsACC oxidase, ACO, germination

© 2020 Mariusz Chojnowski et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Apparent Vmax, Km and Hill coefficient h of ACC oxidase from Callistephus chinensis seeds analyzed in vivo and in vitro at 25 °C

Effect of PVPP and NaHCO3 on in vitro activity of ACC oxidase from Callistephus chinensis seeds germinated for 48 h. Means followed with the same letter are not significantly different at p = 0.05 according to Duncan's test; mean ± SE

Keywords
ACC oxidase, ACO, germination