A. Berczi et H. Asard, NAD(P)H-UTILIZING OXIDOREDUCTASES OF THE PLASMA-MEMBRANE - AN OVERVIEW OF PRESENTLY PURIFIED PROTEINS, Protoplasma, 184(1-4), 1995, pp. 140-144
A considerable number of studies have demonstrated the presence of NAD
(P)-oxidoreductases in the plant and animal cell plasma membranes. Rec
ently several attempts on the isolation and purification of these prot
eins have been presented. The results indicate the presence of distinc
t NAD(P)H-utilizing enzymes in the plasma membrane of several species.
Proteins with molecular masses of 27 kDa, 31 kDa, 36-39 kDa, and 45 k
Da have been identified. Little information is so far available on the
presence and nature of the chromophores on these proteins. The electr
on donor and acceptor specificities of the purified enzymes seem to de
pend to some extent on the purification procedures used. Two interesti
ng remarks became apparent when evaluating the literature available on
this subject. First, although some plasma membrane NAD(P)H-oxidoreduc
tase activity is transmembrane, none of the purified enzymes was repor
ted to depend on the presence of polar lipids to reach full activity.
Second, considerable amounts of enzyme activity were found in the non-
solubilised membrane material and apparently resisted the solubilisati
on procedures. The nature of these activities has not yet been clarifi
ed. Clearly the amino acid sequencing and structural analysis of these
proteins will reveal important new clues to the understanding of the
plasma membrane electron transport in the near future.