Ca. Reddy et Tm. Dsouza, PHYSIOLOGY AND MOLECULAR-BIOLOGY OF THE LIGNIN PEROXIDASES OF PHANEROCHAETE-CHRYSOSPORIUM, FEMS microbiology reviews, 13(2-3), 1994, pp. 137-152
The white-rot basidiomycete Phanerochaete chrysosporium produces ligni
n peroxidases (LiPs), a family of extracellular glycosylated heme prot
eins, as major components of its lignin-degrading system. Upto 15 LiP
isozymes, ranging in M(r) values from 38000 to 43000, are produced dep
ending on culture conditions and strains employed. Manganese-dependent
peroxidases (MnPs) are a second family of extracellular heme proteins
produced by P. chrysosporium that are also believed to be important i
n lignin degradation by this organism. LiP and MnP production is seen
during secondary metabolism and is completely suppressed under conditi
ons of excess nitrogen and carbon. Excess Mn(II) in the medium, on the
other hand, suppresses LiP production but enhances MnP production. Ni
trogen regulation of LiP and MnP production is independent of carbon a
nd Mn(II) regulation. LiP activity is also affected by idiophasic extr
acellular proteases. Intracellular cAMP levels appear to be important
in regulating the production of LiPs and MnPs, although LiP production
is affected,more than MnP production. Studies on the sequencing and c
haracterization of lip cDNAs and genes of P. chrysosporium have shown
that the major LiP isozymes are each encoded by a separate gene. Each
lip gene encodes a mature protein that is 343-344 amino acids long, co
ntains 1 putative N-glycosylation site, a number of putative O-glycosy
lation sites, and is preceded by a 27-28-amino acid leader peptide end
ing in a Lys-Arg cleavage site. The coding region of each lip gene is
interrupted by 8-9 introns (50-63 bp), and the positions of the last t
wo introns appear to be highly conserved. There are substantial differ
ences in the temporal transcription patterns of the major lip genes. T
he sequence data suggest the presence of three lip gene subfamilies. T
he genomic DNA of P. chrysosporium strain BKMF-1767 was resolved into
10 chromosomes (genome size of 29 Mb), and that of strain ME-446 into
11 chromosomes (genome size of 32 Mb). The lip genes have been localiz
ed to five chromosomes in BKMF-1767 and to four chromosomes in ME-446.
DNA transformation studies have reported both integrative and non-int
egrative transformation in P. chrysosporium.