The domain organization in such modules is C-A-T-E.The first module has a three-domain C-A-T organization; these often occur in assembly lines that make N-acylated peptides. The first C domain catalyzes N-acylation of the initiating amino acid (tryptophan) while it is installed on T.  An adenylating enzyme (Ad) catalyzes the condensation of decanoic acid and the N-terminal tryptophan, which incorporates decanoic acid into the growing peptide (Figure 3). The genes responsible for this coupling event are dptE and dptF, which are located upstream of dptA, the first gene of the Daptomycin NRPS biosynthetic gene cluster. Once the coupling of decanoic acid to the N-terminal tryptophan residue occurs, the condensation of amino acids begins, catalyzed by the NRPS.The first five modules of the NRPS are encoded by the dptA gene and catalyze the condensation of L-tryptophan, D-asparagine, L-aspartate, L-threonine, and glycine, respectively (Figure 4). Modules 6–11, which catalyze the condensation of L-ornithine, L-aspartate, D-alanine, L-aspartate, glycine, and D-serine are encoded for the dptBC gene (Figure 5). dptD catalyzes the incorporation of two nonproteinogenic amino acids, L-3-methylglutamic acid (mGlu) and Kyn, which is only known thus far to daptomycin, into the growing peptide (Figure 6). Elongation by these NRPS modules ultimately leads to macrocyclization and release in which an α-amino group, namely threonine, acts as an internal nucleophile during cyclization to yield the 10-amino-acid ring (Figure 6). The termination module in the NRPS assembly line has a C-A-T-TE organization.
Complications
Infection
Repeated trauma
Bursting and reformation
Dysphagia (in the case of a large ranula)

Causes
Minor trauma to the floor of the mouth is thought to damage the delicate ducts that drain saliva from the sublingual gland into the oral cavity. The lesion is a mucous extravasation cyst (mucocele) of the floor of mouth, although a ranula is often larger than other mucoceles (mainly because the overlying mucosa is thicker). They can grow so large that they fill the mouth. The most usual source of the mucin spillage is the sublingual salivary gland, but ranulae may also arise from the submandibular duct or the minor salivary glands in the floor of the mouth. A cervical ranula occurs when the spilled mucin dissects its way through the mylohyoid muscle, which separates the sublingual space from the submandibular space, and creates a swelling in the neck. It may occur following rupture of a simple ranula. Rarely, ranulae may extend backwards into the parapharyngeal space. Mechanism
The fluid within a ranula has the viscous, jellylike consistency of egg white. Diagnosis
The histologic appearance is similar to mucoceles from other locations. The spilled mucin causes a granulation tissue to form, which usually contains foamy histiocytes. Ultrasound and magnetic resonance imaging may be useful to image the lesion. A small squamous cell carcinoma obstructing the Wharton duct may require clinical examination to be distinguished from a ranula. Criteria
Mostly seen in young children and adolescents, both sexes are equally affected. Swelling in floor of mouth, which may be painful. Mostly unilateral, on one side of frenulum.