In bacterial systems, several families of nickel permeases and ATP-dependent nickel carriers have
been characterized. No equivalent mechanism has yet been identified in animals or plants (17)
plant systems, most studies have been conducted at unrealistically high soil-nickel concentrations and
as such may be relevant for nickel toxicity, but are not relevant for nickel uptake under normal conditions.
Cataldo et al. (56)
using 63Ni indicated that a high-affinity Ni2+
carrier functioned at 0.075 or
with a Km
of 0.5μM which approaches the nickel concentration in uncontaminated soils (48)
. Either Cu2+
competitively inhibits Ni2+
uptake suggesting that all the three elements
share a common uptake system (57)
. Uptake at higher nickel-supply levels (0.5 to 30μM) was energy
dependent and had a Km
of 12μM indicative of an active, low-affinity transport system.