Glycolate transporter of the pea chloroplast envelope

Thesis/Dissertation · Tue Jan 01 00:00:00 EST 1985

OSTI ID:6024391

Howitz, K T

The discovery of a glycolate transporter in the pea (Pisum sativum) chloroplast envelope is described. Several novel silicone oil centrifugation methods were developed to resolve the initial rate kinetics of (/sup 14/C)glycolate transport by isolated, intact pea chloroplasts. Chloroplast glycolate transport was found to be carrier mediated. Transport rates saturated with increasing glycolate concentration. N-Ethylmaleimide (NEM) pretreatment of chloroplasts inhibited transport, an inhibition prevented by glycolate. Glycolate distributed across the envelope in a way which equalized stromal and medium glycolic acid concentrations, limiting possible transport mechanisms to facilitated glycolic acid diffusion, proton symport or hydroxyl antiport. The effects of stomal and medium pH's on the K/sub m/ and V/sub max/ fit the predictions of mobile carrier kinetic models of hydroxyl antiport or proton symport (H/sup +/ binds first). The carrier mediated transport was fast enough to be consistent with in vivo rates of photorespiration. The 2-hydroxymonocarboxylates, glycerate, lactate and glyoxylate are competitive inhibitors of chloroplast glycolate uptake. Glyoxylate, D-lactate and D-glycerate cause glycolate counterflow, indicating that they are also substrates of the glycolate carrier. This finding was confirmed for D-glycerate by studies on glycolate effects on (1-/sup 14/C)D-glycerate transport.

• Research Organization: Cornell Univ., Ithaca, NY (USA)
• OSTI ID: 6024391
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
GLYCOLIC ACID
MEMBRANE TRANSPORT
CARBON 14 COMPOUNDS
CENTRIFUGATION
CHLOROPLASTS
PISUM
RESPIRATION
TRACER TECHNIQUES
BACTERIA
CARBOXYLIC ACIDS
CELL CONSTITUENTS
HYDROXY ACIDS
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LEGUMINOSAE
MICROORGANISMS
MONOCARBOXYLIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
PLANTS
RHIZOBIUM
SEPARATION PROCESSES
551001* - Physiological Systems- Tracer Techniques