Biology Reference
In-Depth Information
TABLE I
Main Biochemical Properties of Some Plant Laccases as Compared to Fungal Laccases
MW
(kDa)
Glycosylation
(% or type)
Optimum
pH
Laccases source
pI
References
Acer
pseudoplatanus
115
40
5.2
5.2
Sterjiades et al.
(1992)
Pinus taeda
90
25
5.9
9
Bao et al.
(1993)
Populus
euramericana
90
High manose
type N-glycan
-
9.2
Ranocha et al.
(1999)
45-55
a
Rhus vernicifera
109
120
103
-
8.2
8.6
9.1
Yun-Yang
et al. (2006)
Fungal secreted
laccases
55-85 Up to 25% (3-10
glycosylation
sites)
-
4 Reviewed in
Rodgers
et al. (2010)
a
According to
Nitta et al. (2002)
.
It is generally accepted that plant and fungal enzymes would have distinct
functions. While it is established that fungal laccases are involved in lignin
biodegradation and in detoxification of phenolics, little is known about the
functions of plant laccases. Their capability to polymerize various phenolics to
form insoluble and protective barriers support a protective role and the secreted
laccases from Japanese lacquer tree was suggested to be involved in wound
healing (
Nakamura, 1958
). Similarly, the polymerization of plant phenolics by
laccases was also suggested to contribute to plant defence (
Walker and Ferrar,
1998
). The case study of the laccase-catalysed polymerization of flavonoids in
seeds is discussed in
Section III
.D. For many years, the potential involvement of
laccases in lignin polymerization has been repeatedly proposed (
Bao et al., 1993;
Dean and Eriksson, 1994; Sterjiades et al.,1993
). Indeed, the in vivo laccase-
driven polymerization of plant phenolics, including lignin precursors, has
strongly supported the participation of these enzymes in lignin polymerization,
but without any direct and conclusive evidence, as discussed in the next section.
III. TOWARDS THE FUNCTIONAL
IDENTIFICATION OF PLANT LACCASES
THROUGH FUNCTIONAL GENOMICS
In the past decades, rapid advances in genomic technologies have contrib-
uted to a growing knowledge about the roles of plant laccases. These tech-
nologies include the genome sequencing of various plant species such as
