Amylomaltase is a well-known glucan transferase that can produce large ring cyclodextrins (LR-CDs) or so-called cycloamyloses via cyclization reaction. Amylomaltases have been found in several microorganisms and their optimum temperatures are generally around 60–70 °C for thermostable amylomaltases and 30–45 °C for the enzymes from mesophilic bacteria and plants. The optimum pHs for mesophilic amylomaltases are around pH 6.0–7.0, while the thermostable amylomaltases are generally active at more acidic conditions. Size of LR-CDs depends on the source of amylomaltases and the reaction conditions including pH, temperature, incubation time, and substrate. For example, in the case of amylomaltase from Corynebacterium glutamicum, LR-CD productions at alkaline pH or at a long incubation time favored products with a low degree of polymerization. In this review, we explore the synthesis of LR-CDs by amylomaltases, structural information of amylomaltases, as well as current applications of LR-CDs and amylomaltases.

Treatment of either a pyrido [4,3-d] [1,3]oxazin-4-one or an ethyl 4-amidonicotinate with amines yields a 4amidonicotinamide which may be cyclised by longer contact with the amine, or by heat, to give a pyrido[4,3-d]pyrimidin-4(3H) -one. Some typical infrared and nuclear magnetic resonance spectra are discussed. Birmingham 4 OVER two hundred tetrahydro-and octahydro-pyrido-[4,3-d]pyrimidines have been synthesised as potential diuretic, antirheumatic, and bacteriostatic drugs, but only four fully aromatic pyrido[4,3-d]pyrimidines 293 are known. The parent compound has been prepared3 by treatment of 4-formamidopyridine-3-aldehyde with methanolic ammonia at 100" and pyrido[4,3-d]pyrimidin-4(3H)-one (VI; R1 = R2 = H) (4-hydroxypyrido[4,3-d]pyrimidine) by heating either ethyl 4-aminonicotinate 2 or 4-aminonicotinamide 3 with formamide. The 4-hydroxycompound has been converted into the 4-chloro-2s3 and the 4 -mercapto-pyrido [4,3-d] pyrimidine.2 A restricting factor in the synthesis of this ring system is the length of any route to suitable intermediates bearing either the pyridine or pyrimidine rings. For example 4-aminonicotinaldehyde, which is potentially the most versatile starting material for the preparation of 1-, 2-, or 3substituted derivatives, has been prepared in seven stages from a commercially available compound.3

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The excretion of cyclodextrin glucanotransferase (CGTase) into the culture medium offers significant advantages over cytoplasmic expression. However, the limitation of Escherichia coli is its inability to excrete high amount of CGTase outside the cells. In this study, modification of the hydrophobic region of the N1R3 signal peptide using site-saturation mutagenesis improved the excretion of CGTase. Signal peptide mutants designated M9F, V10L and A15Y enhanced the excretion of CGTase three-fold and demonstrated two-fold higher secretion rate than the wild type. However, high secretion rate of these mutants was non-productive for recombinant protein production because it caused up to a seven-fold increase in cell death compared to the wild type. Our results indicated that the excretion of CGTase is highly dependent on hydrophobicity, secondary conformation and the type and position of amino acids at the region boundary and core segment of the h-region.