Abstract
A p-hydroxycinnamic acid oxidase activity was present in enzyme preparations from first internodes of Sorghum vulgare variety Wheatland milo when incubated in phosphate buffer at pH 7.5. This preparation had no classical polyphenolase activity but had both peroxidase and catalase activities. Since horseradish preparations catalyzed the same reaction, the oxidation probably is another example of a peroxidase-oxidase reaction. A second substrate was p-hydroxyphenylpyruvic acid. Ferulic acid was slightly active at low concentrations and inhibitory at higher ones. Diphenols such as caffeic and chlorogenic acids were inactive and inhibitory to p-hydroxycinnamic acid oxidation. A variety of monophenols such as tyrosine and cinnamic acid were inactive. An active substrate must have a free monophenolic group and para to this a C(3) side chain with a double bond and probably a free terminal acid group. A sulfhydryl reducing agent at the 5 millimolar level such as mercaptoethanol, reduced glutathione, or dithiothreitol was obligatory. Products were varied and were found in both the ethyl acetate-soluble and insoluble fractions after acidification of the incubation mixtures. With internode extracts, about 1 micromole of O(2) was consumed per micromole of p-hydroxycinnamic acid that disappeared in the presence of mercaptoethanol. Tetrahydrafolic acid plus mercaptoethanol were required for a second step oxidation or a parallel reaction; about 2 micromoles of O(2) were consumed per micromole of p-hydroxycinnamic acid that disappeared. Potassium cyanide, diethyldithiocarbamate, ascorbic acid, and ethylenediaminetetraacetate were inhibitory. A similar mercaptoethanol-dependent monophenol oxidase was present in preparations from green shoots that also contained a classical polyphenolase activity. The activity was present in both soluble and particulate (500 to 100,000 gravity) fractions of internodes. Preliminary studies were made of enzyme complexes in the particulate fractions capable of converting phenylalanine and tyrosine to the level of ferulic acid when the above p-hydroxycinnamic acid oxidase was blocked with ascorbic acid. The ratelimiting step was the hydroxylation of p-hydroxycinnamic acid.
Abstract from the paper’s OpenAlex record, shown for indexing and research. Copyright remains with the authors or the publisher. Read at the source ↗
The text the model read, with the source record’s inline markup (italics, sub- and superscripts) rendered and its character entities decoded; quote offsets refer to the raw text.
Claims 13
Claim · model-written summary
A p-hydroxycinnamic acid oxidase activity was present in enzyme preparations from first internodes of Sorghum vulgare variety Wheatland milo when incubated in phosphate buffer at pH 7.5
- Taxon
- Sorghum vulgare
Sorghum bicolore0 - Outcome
- p-hydroxycinnamic acid oxidase activitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A p-hydroxycinnamic acid oxidase activity was present in enzyme preparations from first internodes of Sorghum vulgare variety Wheatland milo when incubated in phosphate buffer at pH 7.5”
Claim · model-written summary
This preparation had no classical polyphenolase activity
- Outcome
- no classical polyphenolase activitye0
SorghumOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This preparation had no classical polyphenolase activity”
t0“Sorghum”
Claim · model-written summary
had both peroxidase and catalase activities
- Outcome
- peroxidase and catalase activitiese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“had both peroxidase and catalase activities”
t0“Sorghum”
Claim · model-written summary
A second substrate was p-hydroxyphenylpyruvic acid
- Outcome
- p-hydroxyphenylpyruvic acide0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A second substrate was p-hydroxyphenylpyruvic acid”
t0“Sorghum”
Claim · model-written summary
Ferulic acid was slightly active at low concentrations and inhibitory at higher ones
- Outcome
- Ferulic acid was slightly active at low concentrations and inhibitory at higher onese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ferulic acid was slightly active at low concentrations and inhibitory at higher ones”
t0“Sorghum”
Claim · model-written summary
Diphenols such as caffeic and chlorogenic acids were inactive and inhibitory to p-hydroxycinnamic acid oxidation
- Outcome
- inactive and inhibitory to p-hydroxycinnamic acid oxidatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Diphenols such as caffeic and chlorogenic acids were inactive and inhibitory to p-hydroxycinnamic acid oxidation”
t0“Sorghum”
Claim · model-written summary
A variety of monophenols such as tyrosine and cinnamic acid were inactive
- Outcome
- tyrosine and cinnamic acid were inactivee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A variety of monophenols such as tyrosine and cinnamic acid were inactive”
t0“Sorghum”
Claim · model-written summary
A sulfhydryl reducing agent at the 5 millimolar level such as mercaptoethanol, reduced glutathione, or dithiothreitol was obligatory
- Outcome
- obligatorye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A sulfhydryl reducing agent at the 5 millimolar level such as mercaptoethanol, reduced glutathione, or dithiothreitol was obligatory”
t0“Sorghum”
Claim · model-written summary
about 1 micromole of O(2) was consumed per micromole of p-hydroxycinnamic acid that disappeared in the presence of mercaptoethanol
- Outcome
- O(2) was consumede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“about 1 micromole of O(2) was consumed per micromole of p-hydroxycinnamic acid that disappeared in the presence of mercaptoethanol”
t0“Sorghum”
Claim · model-written summary
about 2 micromoles of O(2) were consumed per micromole of p-hydroxycinnamic acid that disappeared
- Outcome
- O(2) were consumede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“about 2 micromoles of O(2) were consumed per micromole of p-hydroxycinnamic acid that disappeared”
t0“Sorghum”
Claim · model-written summary
Potassium cyanide, diethyldithiocarbamate, ascorbic acid, and ethylenediaminetetraacetate were inhibitory
- Outcome
- were inhibitorye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Potassium cyanide, diethyldithiocarbamate, ascorbic acid, and ethylenediaminetetraacetate were inhibitory”
t0“Sorghum”
Claim · model-written summary
The activity was present in both soluble and particulate (500 to 100,000 gravity) fractions of internodes
- Outcome
- activity was presente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The activity was present in both soluble and particulate (500 to 100,000 gravity) fractions of internodes”
t0“Sorghum”
Claim · model-written summary
The ratelimiting step was the hydroxylation of p-hydroxycinnamic acid
- Outcome
- hydroxylation of p-hydroxycinnamic acide0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The ratelimiting step was the hydroxylation of p-hydroxycinnamic acid”
t0“Sorghum”