Microbial CYPs

CYPs in bacteria are generally soluble proteins requiring ferredoxin and ferredoxin reductase for the two electrons needed in the CYP catalytic cycle, while CYPs in eukaryotic microbes are typically located in the endoplasmic reticulum with an associated NADPH-CPR providing the necessary reducing equivalents. As such, these are often called class I and class II, respectively (see also 

Different subclasses can occur for the CYPs involved, but class I and class II would give the immediate impression of the type of electron transfer system concerned. 

A further CYP gene has also been cloned that represents a new form. It confers a capability to metabolize the high explosive hexahydro-1,3,5-trinitro-l,3,5-triazine and has been identified in Rhodococcus rhodochrous, with a flavodoxin domain at its N-terminus, but appears also to need a ferredoxin reductase for activity, which may be encoded adjacent to the CYP gene. As this gene contains a flavodoxin domain, this can be placed 

---

The microbial CYP systems were studied at the same time, with yeast CYP being reported by Lindenmeyer and Smith (1964) and bacterial CYP by Appleby (1967) The systems were viewed as models and this was true especially for a CYP from P. putida called P450c, (CYPlOl) that allowed this bacterium to grow on camphor as a carbon source ". In pioneering work from the... 

Studies in yeast have revealed deep insights into eukaryotic processes, and this is also true in studies on CYPs, where the first microbial CYP cloned was found to undertake an ancestral role in the superfamily. That is, CYP51 is needed for sterol biosynthesis and is found in plants, fungi, protists, animals, and some bacteria. ... 

In this chapter, we will outline historical perspectives on the discovery and importance of CYPs in biotechnology before going on to describe the diversity of functions and activities associated with microbial CYPs. The coverage is relatively extensive and is illustrative of the field, but with so many CYPs now revealed it is impossible to discuss each one individually. Obviously many of the CYPs that remain orphan in function today will emerge as being important in future studies. 

A last example to note before moving onto describing the diversity of microbial CYPs and their importance, is provided by the azole antifungal compounds. First developed for agriculture, where they are known as DMI compounds (demethylase inhibitors), these compounds have become central to antifungal therapy in the clinic... 

Although mammalian CYPs are attractive candidates for use as commercial biocatalysts, many functional characteristics limit the opportunities to exploit such a system. Association of the enzymes with membranes prevents easy extraction and purification and limits the opportunities to produce useful recombinant enzymes by cloning the relevant genes for expression in microbial systems. All P450s have a porphyrin-haem active site that requires a second protein to reduce the iron component, often cytochrome P450 reductase or... 

The nomenclature for CYPs is based on eunino acid identity with 40% identity and above needed to place CYPs in the same family and more than 55% to place them in the same subfamily. These rules can be relaxed, as is the case for CYPS Is that can fall below 40% identity, if the CYPs undertake the same function. For microbial eukaryotes, the family numbers 51-69 and 501-699 are available and at the time of writing, numbers up to CYP553 are listed, but each genome reveals many more and many are not yet assigned. Bacterial CYP family numbers are initiated at CYPlOl and a similar expanding scenario can be envisaged with more and more genomes. 

Table 13.1. The Numbers of CYPs in Various Sequenced Microbial Genomes...

Other bacterial CYPs also undertake the breakdown of carbon sources for microbial growth. For instance, CYP 108A1 (P450 gjjp) metabolizes ter-pineol , and CYPl 76A1 (P450 j J can metabolize cineol, while others can metabolize pollutants such as thiocarbamate herbicides and atrazine, as illustrated by CYPl 16 from a Rhodococcus sp. °. The CYP 105 family of streptomycetes especially is associated with a wide variety of xenobiotic... 

The stability of the enzymes is usually greatly enhanced within the protecting environment of the microbial cell because here also enzymes (e.g., catalase and superoxide dismutase) for the detoxification of reactive oxygen species, which might be formed by the CYPs, are present. 

---