Lf. Whitehead et al., ASPARTATE AND ALANINE MOVEMENT ACROSS SYMBIOTIC MEMBRANES OF SOYBEAN NODULES, Soil biology & biochemistry, 30(12), 1998, pp. 1583-1589
Aspartate, alanine and glutamate uptake into bacteroids and symbiosome
s isolated from soybean nodules were measured. An aspartate transport
mechanism was identified in free bacteroids, with an apparent K-m of 2
7.5 mu M and a V-max of 5.14 nmol mg(-1) min(-1). Inhibitor studies in
dicated that aspartate uptake was dependent on a proton motive force a
cross the bacteroid membrane. Aspartate transport was competitively in
hibited by glutamate with an apparent K-i of 9.7 mu M. Alanine uptake
into bacteroids also showed saturation kinetics with a K-m of 12.2 mu
M and V-max of 3.5 nmol mg(-1) min(-1). Bacteroids loaded with (14)Cas
partate exchanged label for external cold aspartate, and glutamate. In
contrast, there was no evidence for aspartate or alanine movement int
o or out of intact symbiosomes except by slow passive diffusion. (C) 1
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