Biology Reference
In-Depth Information
several industrial processes where high enzymatic activity or peculiar stereo-
specificity at low temperature is required. The high specific activity of cold-
adapted enzymes is due to the lack of a number of non-covalent stabilising
interactions, providing improved flexibility of the conformation (
Feller,
2010; Feller & Gerday, 2003; Siddiqui & Cavicchioli, 2006
); this is a key
adaptation to compensate for the exponential decrease in chemical reaction
rates at lower temperatures. For instance, cold-active esterases and lipases
found in the genome of
Ph
TAC125 (
Aurilia, Parracino, Saviano,
Rossi, & D'Auria, 2007; de Pascale et al., 2008; M´digue et al., 2005
)
can be added to detergents for use at low temperatures and to biocatalysts
for biotransformation of heat-labile compounds (
Margesin & Schinner,
1994
). Cold-active Lip1 lipase (
de Pascale et al., 2008
), encoded by the
PSHAa0051
gene, was functionally over-expressed in
Ph
TAC125 at 4
C
(
Duilio et al., 2004
). In contrast, in mesophilic
E. coli
, the recombinant pro-
duction was always found associated with the inclusion bodies and refolding
was unsuccessful (
de Pascale et al., 2008
).
Engineered
Ph
TAC125 expressing a toluene-
o
-xylene mono-oxygenase
from mesophilic
Pseudomonas
sp. OX1 (
Bertoni, Bolognese, Galli, &
Barbieri, 1996
), combined with the endogenous laccase-like protein
induced by copper, can convert several aromatic compounds into non-toxic
metabolites (
Papa, Parrilli, & Sannia, 2009; Parrilli, Papa, Tutino, & Sannia,
2010; Siani, Papa, Di Donato, & Sannia, 2006
). This strategy endows
Ph
TAC125 with degrading capabilities and wide potentiality in bioremedi-
ation applications, for example, removal of organic pollutants from chem-
ically contaminated marine environments and cold effluents of industrial
processes (
Parrilli, Papa, et al., 2010
).
6. P. haloplanktis TAC125 GLOBINS
6.1. General aspects
Three TrHbs were identified in
Ph
TAC125: one TrHbI (encoded by the
PSHAa0458
gene) and two TrHbsII (encoded by
PSHAa0030
and
PSHAa2217
)(
Giordano et al., 2007
). The sequence identity between
TrHbs from different groups is generally low but may be higher within a
given group. The identity between the two TrHbs belonging to group II
is 24%, suggesting that these proteins may have different function(s) in bac-
terial cellular metabolism. Moreover, a FHb, annotated as
PSHAa2880
, has
been found in
Ph
TAC125 (
Giordano et al., 2007
).
The distribution of globins in polar bacteria is very different (
Table 8.3
).