Abstract
The biosynthesis of the tyrosine-derived cyanogenic glucoside dhurrin has been studied with a microsomal preparation obtained from etiolated seedlings of sorghum. The biosynthetic pathway involves tyrosine, N-hydroxytyrosine, and p-hydroxyphenylacetaldehyde oxime as early intermediates (Møller, B. L. and Conn, E. E. (1980) J. Biol. Chem. 254, 8575-8583). The use of deuterium-labeled tyrosine and mass spectrometric analyses demonstrate that the alpha-hydrogen atom of tyrosine is retained in the conversion of tyrosine to p-hydroxyphenylacetaldehyde oxime. This excludes p-hydroxyphenylpyruvic acid oxime as intermediate in the pathway. A high pressure liquid chromatography method was developed to separate the (E)- and (Z)-isomers of p-hydroxyphenylacetaldehyde oxime. The microsomal enzyme system was found to produce initially the (E)-isomer of p-hydroxyphenylacetaldehyde oxime. An isomerase then converts the (E)-isomer to the (Z)-isomer, which is the isomer preferentially utilized by the microsomal enzyme system in the subsequent biosynthetic reactions. The (E)-isomer produced in situ is more efficiently converted to the (Z)-isomer than exogenously added (E)-isomer and may thus be metabolically channeled.
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Claims 8
Claim · model-written summary
Tyrosine alpha hydrogen is retained during conversion to the oxime.
SorghumNot reportedOrgan / stage
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The use of deuterium-labeled tyrosine and mass spectrometric analyses demonstrate that the alpha-hydrogen atom of tyrosine is retained in the conversion of tyrosine to p-hydroxyphenylacetaldehyde oxime.”
e1“etiolated seedlings of sorghum”
Claim · model-written summary
The results exclude p-hydroxyphenylpyruvic acid oxime as a pathway intermediate.
- Taxon
- higher plantsEmbryophytat0
- Compound
- p-hydroxyphenylpyruvic acid oximee0
- Outcome
- excludes p-hydroxyphenylpyruvic acid oxime as intermediatee0
Verbatim
e0“This excludes p-hydroxyphenylpyruvic acid oxime as intermediate in the pathway.”
t0“higher plants”
Claim · model-written summary
A chromatography method was developed to separate the E and Z oxime isomers.
- Outcome
- separate the (E)- and (Z)-isomers of p-hydroxyphenylacetaldehyde oximee0
Not reportedValue
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The biosynthesis of the tyrosine-derived cyanogenic glucoside dhurrin has been studied with a microsomal preparation obtained from etiolated seedlings of sorghum. The biosynthetic pathway involves tyrosine, N-hydroxytyrosine, and p-hydroxyphenylacetaldehyde oxime as early intermediates (Møller, B. L. and Conn, E. E. (1980) J. Biol. Chem. 254, 8575-8583). The use of deuterium-labeled tyrosine and mass spectrometric analyses demonstrate that the alpha-hydrogen atom of tyrosine is retained in the conversion of tyrosine to p-hydroxyphenylacetaldehyde oxime. This excludes p-hydroxyphenylpyruvic acid oxime as intermediate in the pathway. A high pressure liquid chromatography method was developed to separate the (E)- and (Z)-isomers of p-hydroxyphenylacetaldehyde oxime.”
e1“etiolated seedlings of sorghum”
Claim · model-written summary
The microsomal system initially produced the E isomer.
- Outcome
- produce initially the (E)-isomer of p-hydroxyphenylacetaldehyde oximee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The microsomal enzyme system was found to produce initially the (E)-isomer of p-hydroxyphenylacetaldehyde oxime.”
e1“etiolated seedlings of sorghum”
Claim · model-written summary
An isomerase converted the E isomer to the Z isomer.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“An isomerase then converts the (E)-isomer to the (Z)-isomer, which is the isomer preferentially utilized by the microsomal enzyme system in the subsequent biosynthetic reactions.”
e1“etiolated seedlings of sorghum”
Claim · model-written summary
The microsomal system preferentially used the Z isomer in subsequent reactions.
- Outcome
- isomer preferentially utilized by the microsomal enzyme systeme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“An isomerase then converts the (E)-isomer to the (Z)-isomer, which is the isomer preferentially utilized by the microsomal enzyme system in the subsequent biosynthetic reactions.”
e1“etiolated seedlings of sorghum”
Claim · model-written summary
In situ E isomer converted to Z more efficiently than externally added E isomer.
- Outcome
- converted to the (Z)-isomere0
- Direction
- more efficientlye0
- Comparator
- exogenously added (E)-isomere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The (E)-isomer produced in situ is more efficiently converted to the (Z)-isomer than exogenously added (E)-isomer and may thus be metabolically channeled.”
e1“etiolated seedlings of sorghum”
Claim · model-written summary
In situ E isomer may be metabolically channeled.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The (E)-isomer produced in situ is more efficiently converted to the (Z)-isomer than exogenously added (E)-isomer and may thus be metabolically channeled.”
e1“etiolated seedlings of sorghum”