Y-GLUTAMYL PEPTIDES IN PLANTS 9 
ur 
isolated. The data in Tables III and IV show that these peptides occur in tissues 
throughout the plant. Although the iris bulb still contains appreciable quantities of 
the dipeptides during the flowering stage there are sizable amounts distributed 
throughout the plant. They are present in concentrations of the same order of magni- 
tude as the acidic amino acids but considerably higher than glutathione. These data 
give no indication as to where the peptides are being formed and whether they are 
translocated. 
VIRTANEN AND MATIKKALA found y-glutamyl peptides only in the onion bulb and 
not in other parts of the plant. In this plant the peptides are not apparently trans- 
located. 
BREAKDOWN OF Y-GLUTAMYL PEPTIDES 
The previous discussion has emphasized the existence of y-glutamyl peptides in 
diverse tissues of various plants. The metabolism of these compounds should be even 
more interesting since it may give some clue as to their function. 
Since the dry kidney bean seed contained appreciable amounts of y-glutamyl-S- 
methylcysteine (Table II), the changes in the peptide during germination were deter- 
TABLE III 
PEPTIDE AND ACIDIC AMINO ACID CONTENTS OF VARIOUS PARTS OF WEDGEWOOD IRIS PLANTS 
AT THE FLOWERING STAGE 

Quantity of compound* 
(umoles/too atoms of non-protein nitrogen** ) 
y-Glutamyl- 


Tissue Aspartic Glutamic B-amino- y-Glutamyl- Glutathione 
acid acid isobutyric B-alanine 
acid 
Root 23.9 7.00 3.86 1.41 0.099 
Bulb 123 5-70 6.87 1.33 0.00 
Flower stalk 4-30 3.30 1.35 0.76 0.034 
Leaves 8.84 8.96 2.05 0.83 0.017 
* Determinations by quantitative paper chromatography”? after purification”. 
** See footnote** in Table II. 
TABLE IV 
THE DISTRIBUTION AND TOTAL AMOUNT OF y-L-GLUTAMYL-S-METHYL-L-CYSTEINE IN 
GERMINATING ETIOLATED SEEDLINGS OF KIDNEY BEAN (Phaseolus vulgaris ) 

y-Glutamyl-S-methylcysteine* (umoles per plant part) 


Days Cotyledons Hypocotyl Roots Primary leaves Total 
oO 9.02 — — — 9.62 
4 7-05 0.16 0.01 0.02 7.84 
ii 2.68 0.84 0.02 0.09 3.81 
9 1.22 0.74 0.19 0.06 221 

* Measurements made as in Table III. 
References p. 64 
