Biosynthesis labdane

Knoss, W., Reuter, B., and Zapp, J. (1997). Biosynthesis of the labdane diterpene marrubiin in Marrubium vulgare via a non-mevalonate pathway. Biochem J 326(Pt 2) 449-454. 

The responsible compounds include rosenololactone 2 and rosenonolactone 3. Ineketone 4 also has interesting properties, in rice it leads to a reduced ability to germinate. The biosynthesis of R. proceeds through cyclization of a labdane species to a pimarane and subsequent migration of a methyl group. 

Cyr A, Wilderman PR, Determan M, Peters RJ (2007) A modular approaeh for faeile biosynthesis of labdane-related diterpenes. J Am Chem Soc 129 6684-6685... 

GGPP to copalyl diphosphate (CPP), followed by its transformation into abietadiene via 49 in a class I reaction (Scheme 87.20). Notably, the bifunctional plant terpene synthases are generally involved in the biosynthesis of a large superfamily of terpenes, the labdane-related diterpenoids [214]. 

The project to sequence the genome of rice Oryza sativa) has provided a great deal of insight at the genetic level into the production of a host of labdane diterpene phytoalexins. An outline biosynthesis is shown in Figure 3.19 (Mohan et al. 1996). The Type IT cychzation of GGPP and the subsequent Type T ionization of the intermediate labdane diphosphates are catalysed by separate enzymes. The oryzalexin and phytocassane families arise from cychzation of enf-CPP 48 formed by inducible e f-CPP synthases which are distinct from the constitutive ent-CPP synthase involved in GA biosynthesis... 

MacMillan and Beale, 1999). This raises interesting questions for the biosynthesis because the marine plants preceded the terrestrial plants. The labdane derivatives of the two series have many biological properties which include antibacterial, antifungal, anti-inflammatory, anti-parasitic, cytotoxic, and enzyme inhibition (Singh, Pal, and Sharma, 1999). 

Trimusculus only labdane diterpenes. In both genera these derivahves are probably defense allomones against predators and epibiosis. Indeed, they were all isolated from the mucus that covers the animal, and some diterpenes of Trimusculus reticulatus have been shown to repel seastars. The origin of these terpenes (from food, with or without biotransformation, or by de novo biosynthesis) remains imclear, although there are some structural similarities with algal metabolites. Some terpenes from pulmonates are presented in Figure 23.32. 

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