Tunicates patellamides from

Are they involved in the activation and mobilisation of CO2 Van den Brenk et al. suggested this from their studies of patellamide D and ascidiacyclamide, which formed carbonate bridged 2Cu complexes. They suggested that these complexes fix CO2 for use in the formation of CaCOs (used in the internal skeleton of the tunicate).. One argument against this is that marine photosynthetic organisms fix HCOs which is plentiful in seawater (0.002 M). The proposed process, CO2 -> HCOa is therefore the reverse of that expected. 

The cyclamides are small cyclic peptides that characteristically contain multiple thiazole, thiazoline, oxazole, and oxazoline rings, which are derived from cysteine, serine, and threonine residues. Some of the first examples of this class to be described were the patellamides (53-55) from the tunicate Lissoclinum patella, although it was later determined they were produced by the symbiotic cyanobacterium Prochloron sp. The structures were solved by a combination of acid hydrolysis and GC analysis, coupled with 2D NMR. Smaller cyclic peptides from this class include the hexapeptides westiellamide (56) and microcyclamide (57) from M. aeruginosa Many members of the class possess cytotoxic properties, although their biological function or mechanism of action is not fully understood. In contrast to many cyanobacterial peptides, aside from the unusual heterocyclic residues, these peptides generally contain only ribosomal amino acids. 

A review describes the pharmacological properties of l,2-benzisothiazoles. In connection with thiazoles, we find several reviews or papers thiazoles in food aromas patellamides, which are antineoplastic cyclic peptides, from the marine tunicate Lissoclinum patella, which contain an unusual fused oxazoline-thiazole unit and polythiazole-containing peptide antibiotics. An interesting total synthesis of the aglycon of bleomycin A2 should also be mentioned. ... 

Patellamides B and C, Cytotoxic Cyclic Peptides from a Tunicate. 2. Their Real Structures have been Determined by Their Syntheses. Tetrahedron Lett. 26, 5159 (1985). 

In a study of Lissodinum patella harvested in Palau, patellamides A, B and C were not present in the Prochloron sp. symbionts but were scattered in the tunic of the ascidian (Salomon and Faulkner, 2002 Piel, 2004). Later, genetic studies established that patellamides A and C were produced by symbiotic Prochloron (Prochloron didemni) that were isolated from the ascidian and were shown to contain the necessary genes for the formerly considered non-ribosomal but, actually, post-translationally modified ribo-somal biosynthesis of these peptides (Schmidt, Sudek, and Haygood, 2004 Schmidt et al., 2005 Milne et al., 2006 Oman and van der Donk, 2010). 

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