Living on Acetylene. A Primordial Energy Source - The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment - page 15

Chapter 2
Living on Acetylene.
A Primordial Energy Source

Felix ten Brink

Contents
ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

1 INTRODUCTION . . . . . . . . . . . . .............................................................. 16

2 ACETYLENE ............................................................................... 16

2.1 Properties of Acetylene . . ............................................................. 17

2.2 Sources and Bioavailability of Acetylene on Earth and Other Planets . ............ 17

3 BACTERIA LIVING ON ACETYLENE . ................................................ 18

3.1 Pelobacter acetylenicus .............................................................. 19

4 ACETYLENE HYDRATASE FROM PELOBACTER ACETYLENICUS ............... 20

4.1 Biochemical and Spectroscopic Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

4.2 Molybdenum-Substituted Enzyme . . . . . . . . . . ......................................... 21

4.3 Crystallization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

4.4 Structural Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

4.5 Active Site Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.6 Site-Directed Mutagenesis . . . . . . . . . .................................................. 25

4.7 Density Functional Theory Calculations on the Substrate
Binding Mode and Amino Acid Protonation States ................................. 27

4.8 Towards the Reaction Mechanism ................................................... 28

5 CONCLUSIONS ............................................................................ 32

ABBREVIATIONS AND DEFINITIONS ..................................................... 33

REFERENCES . ................................................................................. 34

Abstract The tungsten iron-sulfur enzyme acetylene hydratase catalyzes the
conversion of acetylene to acetaldehyde by addition of one water molecule to
the C C triple bond. For a member of the dimethylsulfoxide (DMSO) reductase

family this is a rather unique reaction, since it does not involve a net electron