Insect Molecular Biology and Biochemistry

Chitin Metabolism in Insects Part 5

Enzymes of Chitin Metabolism Enzymes of chitin metabolism, including some members of the chitinase and chitin deacetylase families, have the ChtBD2 motif (Kramer et al., 1993; Campbell et al., 2008; Dixit et al., 2008; Zhu et al., 2008a). The presence of one or more copies of this ChtBD2 motif has been suggested to increase the […]

Insect CYP Genes and P450 Enzymes Part 1

Introduction Overview Cytochrome P450, or CYP genes, constitute one of the largest family of genes, with representatives in virtually all living organisms, from bacteria to protists, plants, fungi, and animals (Werck-Reichhart and Feyereisen, 2000). An ever-growing number of P450 sequences is available, and the role of P450 enzymes is being documented in an increasing number […]

Insect CYP Genes and P450 Enzymes Part 2

CYPome Evolution The main driver of CYPome evolution is of course gene duplication, followed by divergence (by neofunctionaliza-tion or subfunctionalization) or death (pseudogenization or deletion) (review in Feyereisen, 2011); many mechanisms can generate paralogous genes in the CYPome. These include tandem duplications, including unequal crossing over of various lengths, transposable element-induced non-allelic recombinations, and chromosome […]

Insect CYP Genes and P450 Enzymes Part 3

P450 Enzymes P450 Protein Structure The sequence identity of distantly-related P450 proteins can be as low as that predicted from the random assortment of two sets of 500 or so amino acids. This is because there are very few absolutely conserved amino acids; in fact, only one is absolutely conserved, the Cys ligand to the […]

Insect CYP Genes and P450 Enzymes Part 4

Substrate Selectivity and Homology Models of P450 Enzymes Metabolism of a substrate by a P450 enzyme produced in a heterologous system is first a qualitative description of substrate selectivity. A negative result, when it is reported, should be interpreted with more caution. It can take considerable effort to achieve optimal reaction conditions, and this can […]

Insect CYP Genes and P450 Enzymes Part 5

P450 Functions Ever since the pioneering work of Agosin and Terriere in the early 1960s on microsomal enzymes that hydroxyl-ate DDT and naphthalene (review in Agosin, 1985), the enzymes now recognized as P450 have been best known for their role in xenobiotic metabolism in insects. They are often denoted as "detoxification enzymes." This designation not […]

Insect CYP Genes and P450 Enzymes Part 6

P450 and juvenile hormone metabolism The landmark chemical feature of juvenile hormones is the presence of the epoxide group, and it is well established that epoxidation of the JH precursors in the corpora allata (CA) is catalyzed by a P450 enzyme. The biochemical evidence was presented in two studies on the allatal enzyme, one with […]

Insect CYP Genes and P450 Enzymes Part 7

Xenobiotic Metabolism: Activation and Inactivation Natural products The metabolism of plant toxins by insects has been reviewed extensively (see, for example, Brattsten, 1979b; Dowd et al., 1983; Ahmad, 1986; Ahmad et al., 1986; Mullin, 1986; Yu, 1986; Li et al. , 2007). Relatively few studies have directly assessed the role of P450 enzymes in the […]

Insect CYP Genes and P450 Enzymes Part 8

P450 and Host Plant Specialization The Krieger hypothesis and beyond The interactions of plants and insects, and, more specifically, the role of plant chemistry in the specialization of phytophagous insects have generated a vast literature. Figure 23 Chlorfenapyr and cypermethrin metabolism. The same P450 in Heliothis virescens probably activates the pyrrole and inactivates the pyrethroid, […]

Insect CYP Genes and P450 Enzymes Part 9

Insecticide Resistance Phenotype, genotype, and causal relationships Insecticide resistance is achieved in a selected strain or population: (1) by an alteration of the target site; (2) by an alteration of the effective dose of insecticide that reaches the target; or (3) by a combination of the two. The resistance phenotypes have long been analyzed according […]

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