Localization of Sepiapterin Deaminase and Pteridines In the Granules In Epidermal Cells of the Silkworm, Bombyx mori

Abstract

SummaryA new method for assay of sepiapterin deaminase (3.5.4.24) activity by use of high performance liquid chromatography (HPLC) was developed. By this sensitive method the enzyme activity in the cell organelle was assayed. After cell fractionation, the enzyme was extracted with deoxycholate from pteridine granules of epidermal cells of the lemon mutant silkworm. On stepwise sucrose gradient centrifugation, most of the enzyme activity localized in the aggregated pteridine granules fraction, while the soluble fraction contained only one fourth of the total enzyme activity. The enzyme in the granule fraction had the same properties as the previously reported sepiapterin deaminase. These data show that the enzyme is localized in pteridine granules in the living cells. The attachment of the enzyme to the granule membrane is rather loose and previous papers studied the enzyme released from the granules.Cell fractionation and morphological observation showed that sepiapterin, sepialumazine and other pteridines were also localized in the granules together with uric acid.

Expression of one isoform of GTP cyclohydrolase I coincides with the larval black markings of the swallowtail butterfly, Papilio xuthus

“…Pteridines are contained in the larva of lepidopteran species (Tsusue´et al, 1990;Sawada et al, 1998). Pteridines are considered to be contained in the white region of young larva of P. xuthus; however, the correlation between GTPCHI expression and the white region was not found in our study.…”

Pigment pattern formation in the quail mutant of the silkworm, Bombyx mori: parallel increase of pteridine biosynthesis and pigmentation of melanin and ommochromes

“…The quail mutant accumulated a larger amount of sepialumazine in the integument in comparison with the background strain (Figure 4), indicating that there may be a certain link between melanin, ommochromes and pteridines. It has been reported that in silkworms sepialumazine, which is formed by hydrolytic deamination of sepiapterin (Sawada et al, 1998;Tsusué et al, 1990), in combination with xanthommatin, are key pigments responsible for color variations in the epidermis (Ohashi et al, 1983b). Sepiapterin which has thus far only been detected in the lemon mutant of the silkworm (Mazda et al, 1980;Ohashi et al, 1983b) has not been detected in both silkworms used for this study (data not shown).…”

1. Integument

“…Pigmentary colours are due to the selective absorption by chemical substances. Such substances have been studied extensively in Bombyx larvae (Ohashi et al 1983(Ohashi et al a, 1983Sawada et al 1990;Tsusue et al 1990): black colours or patterns are due to melanine in the cuticle, yellow and pink colours are due to pteridines and ommochrome in the form of sepialumazine and xanthommatine. The reddish epidermis has large amounts of these two pigments.…”