Utilization and synthesis of glutamine in the lens
Previous studies with rat and calf lenses have shown that the primary source of lenticular glutamate for a wide variety of pathways is glutamine, which is more readily transported from the surrounding fluids than glutamate. In contrast, recent studies showed that monkey lenses utilize glutamate more rapidly than glutamine, although glutamine appears to enter monkey lenses more rapidly than glutamine. Further studies were initiated to elucidate the balance between transport, deamidation, and synthesis of glutamine in the lens. Glutamine synthesis in intact rat lenses was barely detectable; however, homogenates of adult rat lenses converted measurable amounts of (/sup 3/H)-glutamate to glutamine. The identity of the product was confirmed using glutaminase. Glutamine deamidation in intact rhesus monkey lenses incubated in TC-199 medium containing 2 mM glutamine was only 0.19 ..mu..mol g/sup -1/ hr/sup -1/, compared with 1.96 ..mu..mol g/sup -1/ hr/sup -1/ for rat lenses under identical conditions. However, under optimal assay conditions, glutaminase activity in monkey lens homogenates was similar to that of rat lens homogenates. Thus, the rate of synthesis and deamidation of glutamine by intact lenses is apparently limited factors other than total lenticular glutamine synthetase and glutaminase activity.
- Research Organization:
- Univ. of Tennessee, Memphis
- OSTI ID:
- 6180434
- Report Number(s):
- CONF-870644-; TRN: 87-033965
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 46:6; Conference: 78. annual meeting of the American Society of Biological Chemists conference, Philadelphia, PA, USA, 7 Jun 1987
- Country of Publication:
- United States
- Language:
- English
Similar Records
Glutamine domain of the chimeric protein, CAD, that initiates pyrimidine biosynthesis in mammalian cells
Uptake and metabolism of L-(/sup 3/H)glutamate and L-(/sup 3/H)glutamine in adult rat cerebellar slices
Related Subjects
AMIDASES
ENZYME ACTIVITY
GLUTAMIC ACID
METABOLISM
GLUTAMINE
BIOSYNTHESIS
BIOLOGICAL PATHWAYS
CRYSTALLINE LENS
HOMOGENATES
MONKEYS
RATS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
AMIDES
AMINO ACIDS
ANIMALS
BODY
BODY AREAS
CARBOXYLIC ACIDS
ENZYMES
EYES
FACE
HEAD
HYDROLASES
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
MAMMALS
NON-PEPTIDE C-N HYDROLASES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PRIMATES
RODENTS
SENSE ORGANS
SYNTHESIS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques