SUMMARY The metabolism of glycyl-L-leucine in a leucine auxotroph of strain K-12 was investigated with respect to the bacteriostatic effect of the peptide on growth, its hydrolysis by bacterial preparations, and its uptake by resting organisms. Growth inhibition by the peptide is relatively small if the organisms used as the inocula for the growth tests are taken from actively multiplying cultures (young organisms), but is marked if the inocula consist of organisms from cultures aged in an acid-producing, poorly buffered medium; ageing in a well-buffered or neutral medium does not produce peptide-sensitive organisms. Aged organisms that are very sensitive to the peptide readily take up the compound from the external medium, both in the absence and presence of chloramphenicol. Whole-cell preparations of these aged organisms do not effect the rapid hydrolysis of glycylleucine, but cell-free extracts have as much enzymic activity as cell-free extracts of young organisms. Whole-cell preparations of young organisms also have high enzymic activity. The available data suggest that the uptake of glycylleucine by young organisms is followed immediately by its hydrolysis, whereas the peptide taken up by aged (peptide-sensitive) organisms is hydrolysed only very slowly. The growth of inocula composed of organisms taken from yeast extract + peptone + agar slopes is markedly inhibited by glycylleucine. The hydrolytic activity of whole organisms taken from slopes is significantly less than that of young organisms, but disruption of slope-grown organisms to produce cell-free extracts does not lead to any significant increase in enzymic activity.


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error