Skip to Main Content

Dr. Rachel Austin

Barnard College – Department of Chemistry

September 27, 2019 – Fall Seminar

Time and Location: 12 Noon in Meyerhoff Chemistry Building, Room 120

Host: Dr. Aaron Smith

Catalytic activity of non-heme diiron alkane monooxygenases

 Alkane hydroxylase (AlkB) is a membrane-spanning non-heme diiron enzyme with a histidine-rich coordination site, first identified about 50 years ago, responsible for catalyzing the hydroxylation of the majority of medium-to-long straight chain alkanes in the environment. AlkB catalyzes the hydroxylation of terminal alkanes, the epoxidation of alkenes, and, in selected cases, the desaturation of alkanes.  Despite its importance in the global carbon cycle, relatively little is known about this large, widely-distributed and important class of hydroxylases.  We have studied the reaction mechanism and substrate specificity of AlkB fromm Pseudomonas putida GPo1 with a range of substrates.  More recently we have cloned and purified AlkB from 4 additional organisms:  the marine organism Alcanivorax borkumensis AP1, Dietzea cinnamea, Thermomonospora curvata, and Mycobacterium tuberculosis as well as a related enzyme xylene monooxyganseFunctional studies on these non-heme diiron hydroxylases, interpreted in light of recently published crystal structures of two related enzymes, the fatty acid desaturase steroyl-CoA desaturase[1][2] and sphingolipid a-hydroxylase (Scs7p), a yeast homolog of fatty acid 2-hydroxylase (FA2H)[3], answer some questions about structure-function relationships in this important class of metalloenzymes and raise others.

[1] Bai, Y., McCoy, J. G., Levin, E. J., Sobrado, P., Rajashankar, K. R., Fox, B. G., and Zhou, M. (2015) X-ray structure of a mammalian stearoyl-CoA desaturase. Nature 524, 252–256

[2] Wang, H., Klein, M. G., Zou, H., Lane, W., Snell, G., Levin, I., Li, K., and Sang, B. C. (2015) Crystal structure of human stearoyl-coenzyme A desaturase in complex with substrate. Nat. Struct. Mol. Biol. 22, 581–585

[3] Guangyu Zhu, Mary Koszelak-Rosenblum, Sara M. Connelly, Mark E. Dumont, and Michael G. Malkowski (2015) The Crystal Structure of an Integral Membrane Fatty Acid a-Hydroxylase, J. Biol. Chem. 290, 29820-29833