passages.id: split_5_test_3425_passage
passages.type: progene_text
passages.text: When speF ( which encodes ornithine decarboxylase ) and proB ( which encodes gamma-glutamyl kinase ) were inactivated to prevent the conversion of L-ornithine to putrescine and to block the biosynthesis of a side branch of L-ornithine , respectively , L-ornithine production was further enhanced approx. 140 % from 5.5 to 13.2 mg / g ( dry cell weight ) .