60 J. F. THOMPSON et al. 
mined (Table IV). There was a considerable net loss of peptide during 9 days of germi- 
nation even though there may have been a concomitant synthesis taking place. 
RINDERKNECHT ef al.® have also reported a disappearance of this peptide during the 
germination of Lima bean seeds. Presumably hydrolysis had taken place. In the break- 
down of glutathione in purified swine-kidney preparations?’, the first step is trans- 
peptidation?** followed by hydrolysis of the resultant cysteinylglycine as indicated 
below: 
transpeptidase 
glutathione + amino acid <~—_,_ y-glutamyl amino acid + cysteinylglycine 
peptidase 
cysteinylglycine + H,O0 ~~ cysteine + glycine 
Although transpeptidation may account for the disappearance of y-glutamyl-S- 
methylcysteine during germination, this process appears unlikely because there was 
no concomitant increase in other acidic peptides. Transpeptidation alone would result 
in no net decrease in y-glutamyl peptides. HIRD AND SPRINGELL®? have shown that 
y-glutamyl transpeptidases from sheep kidney transfer y-glutamyl groups to water 
or amino compounds depending on the conditions. However, with a more purified 
enzyme preparation, BINKLEY?’ observed no hydrolysis under any conditions. Since 
there is some evidence for a transpeptidase and hydrolytic activity in bean extract 
(see below), a mechanism for peptide breakdown can be visualized. The ordinary 
proteinases and peptidases do not act on y-glutamyl peptide bonds. A cell-free pre- 
paration from Bacillus subtilis*4 which hydrolyzes y-glutamyl polypeptides has not 
been observed in higher plants. Hence it seems unlikely that the enzymes which are 
hydrolyzing the proteins of the cotyledons of the germinating bean are also hydro- 
lyzing y-glutamyl-S-methylcysteine. 
Microorganisms appear to have an enzyme for the hydrolysis of the y-glutamyl- 
cysteine bond but not other y-glutamyl bonds. Hac, SNELL AND WILLIAms® found 
that glutathione can substitute for glutamic acid in the growth of L. arabinosus. We 
have confirmed this observation and extended the test to the first two y-glutamyl 
TABOR Vi 
THE UTILIZATION OF y-GLUTAMYL PEPTIDES BY Lactobacillus avabinosus* 


Optical density at 560 mu 


Compound (umoles of compound per tube) 
o 0.1 0.2 0.6 r.0 
L-Glutamic acid 0.008 0.012 0.106 0.272 0.377 
Reduced glutathione 0.008 0.007 0.012 0.211 0.360 
y-Glutamyl-S-methylcysteine —- —— — _ 0.028** 
y-Glutamyl-f-aminoisobutyric acid — — — = 0.008 

* Each tube had 2.5 ml of the medium of Hac, SNELL AND WILLIAMs** without glutamic acid 
and glutamine. Samples were incubated 26 h at 37° and then diluted with 5 ml of water for absorb- 
ancy reading. 
** 3 weeks incubation. 0.4 wmole of glutamic acid gave an absorbancy of 0.186. 
References p. 64 
