Presentation is loading. Please wait.

Presentation is loading. Please wait.

Psychrophiles: a challenge for life

Similar presentations

Presentation on theme: "Psychrophiles: a challenge for life"— Presentation transcript:

1 Psychrophiles: a challenge for life
Laboratory of Biochemistry Belgium Punta del Este, May 2010

2 Arrhenius law: Thermodependence of reaction rate
k=A. exp (–Ea/RT) k Q10=VT+10/VT=2-3 T(°C) 10 20 30 40 50

3 How do psychrophiles maintain appropriate rate of reactions ?

4 How do psychrophiles, living below 0°C, prevent freezing?

5 Cells and extracellular ice

6 Bacteria in liquid veins of sea ice


8 General properties of enzymes from psychrophiles
High specific activity at low and moderate temperatures High thermosensitivity - Flexible structure

9 Specific activities of psychrophilic(blue) and mesophilic(green) enzymes as a function of temperature PPA AHA On this plot, you can see the effect of temperature on the activity of two homologous enzymes: AHA is the alpha-amylase from Pseudoalteromonas haloplanktis, an antarctic bacteria; and PPA is the alpha-amylase from the pig pancreas. This graph reveals 3 basic features: 1. Psychrophiles synthesise enzymes with higher specific activity at low temperatures. 2. The apparent maximal activity is shifted toward low temperatures, reflecting their weak thermostability. 3. The adaptation is apparently not complete. The specific activity displayed by the psychrophilic enzymes around 0°C remains lower than that of the mesophilic at 37°C.

10 Growth of an Antarctic bacterium (left) and excretion of α-
Growth of an Antarctic bacterium (left) and excretion of α amylase (right) as a function of temperature α-amylase Growth α- α- 4°C 4°C 18°C 25°C 18°C 25°C 25°C

11 Antifreeze GlycoProtein(AFGP)
β-galactosyl-1, 3,-α-N-acetyl glucosamine


13 Animation of the process of ice recrystallization

14 Some cryoprotectants Glucose Tréhalose Sorbitol Ribitol Glycérol

15 Effects of cryoprotectants
1- They depress the freezing point of water 2-They prevent cell dehydration when extracellular ice is present 3-They protect proteins against cold denaturation

16 Homogeneous ice nucleation Heterogeneous ice nucleation
Water molecules Homogeneous ice nucleation (-39°C) Heterogeneous ice nucleation (>-5°C) INP ANP Stimulation Inhibition O Ice crystals AFP (IR) Growth inhibition and recrystallization inhibition

17 Effects of ice-nucleating proteins
1-Ice is confined in the extracellular space 2-The formation of ice is controlled by the organism (time) 3-At the same time production of cryoprotectants 4-Some water is lost contributing to decrease the freezing point in the intracellular space

18 INP ANP Stimulation Inhibition O Ice crystals AFP (IR) Water molecules
Homogeneous ice nucleation (-39°C) Heterogeneous ice nucleation (>-5°C) INP ANP Stimulation Inhibition O Ice crystals AFP (IR) Growth inhibition and recrystallization inhibition

19 b: protein concentration
Biodegradation of polluted water by Arthrobacter psychrolactophilus at 10°C Turbidity Open symbols: sterilized Black symbols: with strain a: turbidity Proteins b: protein concentration c: amino acids d: simple sugars Amino acids Simple sugars

20 Psychrophiles and cold-active enzymes in Biotechnology
Applications Advantage Involved enzymes Detergents Washing at low temperature Protease, lipase, amylase, cellulase, oxygenase Food industry Improved taste and aroma of fermentation products (cheese,etc) Fermentation and ripening enzymes Lactose hydrolysis Β-galactosidase Juice clarification and yield of extraction Pectinase, cellulase Meat tenderization Protease Organic synthesis Volatile and heat-sensitive compounds, organic phase synthesis Protease, lipase, glycosyl- hydrolase, etc Molecular biology Mild inactivation, ligation, PCR Various enzymes Low temperature Ligation, carry-over in PCR Textiles Improved quality due to mild heat treatment for desizing, bio-polishing and stone- washing of fabrics Amylase, laccase, cellulase Environment In situ bioremediation of organic pollutants and hydrocarbons Various hydrolases, mono- and-dioxygenases, dehydrogenases Biogas production Psychrophilic anaerobic digestion

21 Lactose splitting catalysed by beta-galactosidase (lactase)
Lactozym(Novo), Maxilact(Gist Brocades)

22 Tests in milk at 5 °C ß-galactosidase
Tests in milk at 5 °C ß-galactosidase Lactose + H2O D-glucose + D-galactose   Gal-DH D-galactose + NAD D-galactonolactone + NADH + H+ -galactosidase [Lactose ] Free[D-galactose] [Lactose] hydrolysed (mg/l) (mg/l) (mg/l) P. haloplanktis Maxilact

23 Isomerisation of D-galactose into D-tagatose (sweetener)
Ca(OH)2 D-galactose D-tagatose

24 3D – Structure of cold-adapted xylanase
The structure determined is shown here and can be described as a distorted (α/α)6 barrel, that is, it consists of six inner helices and six outer helices in addition to a number of beta strands. The active site is located in a long acidic cleft running across the molecular surface at the N-terminal end of the inner helices with the the N and C termini being located on the opposite side of the structure to this. Clearly, this structure is very different to that described for the family 10 and 11 xylanases but is similar to that for the family 8 endoglucanase CelA. Family 8 Endoglucanase CelA Family 11 Xylanase Family 10 Xylanase

25 Cold xylanase in baking
Xylanase Xyl/Kg Loaf Vol Cut Width (IU) (ml) (mm) 1 Control 2 Belase 3 pXyl 4 pXyl

26 J-S Dumont d’Urville (Terre Adélie)

27 Acknowledgments Academic: Richard Haser (Lyon):X-ray crystallography
Nick Russell (London): Microbiology, Biochemistry Luisa Tutino (Naples): Expression in psychrophiles Rosa Margesin (Innsbruck): Biotechnology Rick Cavicchioli (Sydney): Microbiology, Biochemistry Jozef Van Beeumen (Gent): Biochemistry, Crystallography Philip Thonnart (Gembloux): Biotechnology Industrial: Beldem-Puratos (Belgium): Thierry Dauvrin and Jacques Georis Nutrilab (Belgium): In the Antarctic ( J-S Dumont d’Urville and Kerguelen): Expeditions polaires francaises In the Arctic (Ny-Alesund-Dirigible Italia): CNR (Italy)

Download ppt "Psychrophiles: a challenge for life"

Similar presentations

Ads by Google